Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/1958754.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Supernatural
  Relationship:
      Castiel/Dean_Winchester
  Character:
      Castiel_(Supernatural), Dean_Winchester, Sam_Winchester
  Additional Tags:
      teacher!Cas, Student!Dean, Underaged!Dean, Top!Cas, bottom!Dean, First
      Time, Blow_Jobs, Maths_(sorry), Rimming, Anal_Sex, Anal, Anal_Fingering,
      Light_Dom/sub, Dom!Cas, Sub!Dean, PWP, Porn_Without_Plot, Plot_What_Plot,
      AU_-_alternate_universe, Shameless_Smut, Smut, Dirty_Talk, Castiel_Talks
      Dirty, Spanking, Math_Kink
  Series:
      Part 1 of Math_is_Fundamental
  Stats:
      Published: 2014-07-15 Words: 3632
****** Illegal ******
by Just_Breezy
Summary
     When Castiel accepted a job as a high school math teacher, he assumed
     his greatest plight would be trying to get students to conceptualize
     the abstract equations, but no, Castiel has spent weeks, weeks of
     being perpetually rock hard and flush while desperately trying to get
     through 80-minute blocks. Mr. Dean Winchester is a gifted, very
     seventeen-year-old student with iridescent green eyes and a mouth
     begging to be fucked and an ass to match. The worst part? Castiel is
     about to break; there are only so many times he can feign irritation
     with Dean’s persistent advances, and only so many times he can beat
     off in his room after class.
Notes
     This is my first time writing an alternate universe, I don't really
     like how it's written and flows, but smut is smut, right....?
     Haha, anyways, please tell me what you think in the comments, what I
     can improve on, and if I should do a fic where Cas shows Dean his
     cuff :/ :)
     I hope you enjoy, and as always, I'm sorry!
    When Castiel accepted a job as a high school math teacher, he assumed his
greatest plight would be trying to get students to conceptualize the abstract
equations, but no, Castiel has spent weeks, weeks of being perpetually rock
hard and flush while desperately trying to get through 80-minute blocks. The
reason being a student in his grade 12 calculus class seems to have made it his
mission to make Castiel pop the button of his jeans during class. Mr. Dean
Winchester is a gifted, very seventeen-year-old student with iridescent green
eyes and a mouth begging to be fucked and an ass to match. The worst part?
Castiel is about to  break; there are only so many times he can feign
irritation with Dean’s persistent advances, and only so many times he can beat
off in his room after class.
    After a particularly heated class, Castiel asked that Dean stay after class
for a word. Castiel sat at his desk, looking over the assignments the students
had just handed in. He had only spent half the class today going over Riemann
Summations, the rest of the time the students were to work on any missing tests
or homework. Dean used this time to lick his lips lasciviously, run his hand
over the tight crotch of his jeans, and even going so far as to undo the button
of his jeans. Dean smiled iniquitously as he sauntered up to the desk just as
the final student shuffled out of the room, closing the door behind him.
Slowly, the trickling sound of students leaving for their weekend adventures
faded.


“Dean, why do you insist on making classes difficult for me, or continuing
these advances? I could lose my job just for you flirting with me.”
“I have a thing for blue eyes and smart guys.”
“I’m almost twice your age, you’re my student, you’re- !”
“Not going to give up until you give in, and I know that’s going to be soon. I
can almost see your cock throb under that denim when I lick my lips; I watched
you devour me while I rubbed my cock through my jeans, there’s no denying you
want me, and there’s nothing stopping you.”


    The sentence hung in the thickening air as tension built between the two.
Dean’s boldness only grew as he moved slowly to behind the desk where Castiel
sat. Before Dean could proceed any further, Castiel sprang up and pulled the
boy by the collar of his shirt, spinning him around and assailing his entire
body taut between himself and the board. The younger boy’s breath hitched as he
grew achingly hard from the inimical barrage.

    “Do you think this is a game?! That this behavior is ok?!” Castiel’s
frustrations tainted his words with more enmity than carnality. He dropped his
head momentarily, resting on Dean’s collarbone. Castiel took a deep breath,
dropping his hands to his sides and stepping away from the student. Dean seemed
to be in complete shock, having no clue whether the throbbing erection in his
pants was called for or not, he stood completely still, all bravado gone.

    Castiel didn’t seem to notice Dean’s shock, as he leaned over his desk,
searching in the top drawer; “you have been very misbehaved in class, you
constantly interrupt me while giving a lesson, you cannot answer a question
without turning it into some sexual warfare, you parade yourself around in
tight fitting clothing and bend over to show off that perfect ass of yours. You
drive me crazy every day; I have never been this hard for this long.” Castiel’s
voice never faltered, his gravelly baritone shaking Dean out of his veneration,
regaining some of his bluster.
    “You love watching me-“, before Dean could finish what was clearly going to
be a well-thought out snarky comment, Castiel looked up from his desk drawer,
pulling out a bottle of lube. “This is not some sort of recreational fuck, Mr.
Winchester. Naughty boys need to be punished, and as you have done nothing in
class but incessantly tease me, we will also make this a learning experience,
and we will begin by setting some ground rules: there will be no speaking
unless spoken to, there will be no touching unless allowed, any disobedience
will result in spanking and if you cannot follow the rules, I will use my
handcuffs.” Castiel’s smoky voice can make anything sound assertive, and Dean
finally knew where it stemmed from; Mr. Novak was a complete dom in the sack.
    Dean sported an exceptional hard on as Castiel turned around holding the
lube to face his student. “For all the pain you’ve caused me throughout class
there will be an additional punishment, but that will come after,” Castiel
glared at Dean through his execrable blue eyes; “first, Mr. Winchester, you
will strip for me.” The command in his tone left no room for argument. This, of
course is not the Winchester-way. Before Dean began to undress, he cocked an
eyebrow, “what are you going to do, Cas? You’re like half-“ “you should show me
some respect, and you can begin by calling me sir.” Dean will- or rather would
never admit to himself just how much of a sub he really is, but being told what
to do in that voice made of gravel and smoke could get him to do (and admit)
anything. Castiel sat down on the wearing leather chair and placed the bottle
of lube on the desk, relaxing for the little show he was about to enjoy. Dean
shifted almost uncomfortably under Castiel’s scrutiny. He would deny to anyone
that asked how much he enjoyed the humiliation of putting on a strip tease for
anyone, but seeing the hunger in Castiel’s eyes made precum leak through his
tight boxers, as he pulled his green t-shirt over his head, extending his abs
and arms, presenting his body for Castiel; Castiel licked his lips at the
morsel he was about to devour. Dean slid his hands down his taut torso, giving
small ministrations to his firm nipples and moaning at his own hands as he
continued further south. Next came the all-too-tight jeans and boxers in one
go, Dean purposely bent toward the class as he discarded his jeans, showing off
his ass and tight hole to the teacher, imagining there was a class of students
watching them. The air was cool against his exposed skin, cooling the vibrant
blush that painted his body.
   Thank god for Castiel’s self-control, had anyone else been presented with
the effigy Dean made standing naked in a classroom, hands unable to touch his
leaking cock, trying to find relief in other frictions, they would destroy Dean
right there, without dragging it out, without making this a learning experience
for the boy.    “Now, come here,” “yes sir” he emphasized the ‘sir’ just to irk
Castiel without breaking any of the rules. Dean stood at attention in front of
his teacher, cock on display for the older man. Castiel moved forward in his
chair, allowing more room on his legs; “on my lap, it’s time for your
punishment.” Dean hesitated, but understood: he pressed his toned stomach
against the coarse fabric of his teacher’s trousers, ass in the air.

“You’ve been very naughty, and as your teacher it’s my job to ensure you learn-
““I doubt the schooling system had this in mind when-“, Dean was cut off by
three harsh hits to his right and left cheeks. Dean could feel where handprints
bloomed. “What are the rules, Dean?” Dean didn’t speak, pleased with himself
for not breaking the ‘no talking rule’ again. In the moment of extended
silence, he was greeted with three harder slaps, “disobedience will be
punished, and we cannot forget about the discipline waiting for your classroom
indiscretions. Any more broken rules and I won’t let you come today, Mr.
Winchester, understood?” Dean was beginning to lose himself in the blurring
lines of pain and pleasure as more handprints painted his reddening ass.
Finally, Dean realized where he went wrong; averting the hits Castiel was
preparing to give, “no speaking, unless spoken to”. Castiel smiled as Dean
dropped in head against the older man’s thigh, “right, Dean” Castiel cooed as
he ran a dry finger over Dean’s tense hole, followed by five more aggressive
hits. The spanks came on alternating cheeks with varying intensity; there was
no rhythm Dean could pick up on to prepare for.

   After what felt like twenty slaps, both Castiel and Dean were breathless
from the contentious onslaught. “My, my, what a good little boy”, Castiel
huffed out while rubbing gentle circles onto Dean’s abused ass. Dean clutched
at Mr. Novak’s thighs, desperately wanting to touch and taste the erection he
could feel tickling his side, wanting to prove what a good little boy he could
be. His own hard on destroying the outside of Castiel’s pants, rubbing precum
all over the fabric.

   “Now for the learning portion, stand up Mr. Winchester”, Dean mewled at the
loss of contact on his ass, but stood up next to the desk at attention while
Castiel wrote an equation on the board. “We shall begin with something simple:
f(x) = x² + 2, where a = -2 and b = 1.” Dean was completely transfixed on the
graceful movement of Mr. Novak’s hand, wanting for that hand to be dancing over
him. “Dean, if you cannot focus, you will not be allowed to come today, do you
understand?” The aggravation in his voice pulled Dean back to the situation,
“yes, sir.” Dean looked at the equation again and asked for the chalk. As Dean
began writing out the summation, Castiel quietly watched while lubing up his
fingers. He softly moved next to Dean, and tenuously pressed his index finger
up to the first knuckle. Dean shuttered, drawing right through his work at the
intrusion. As Castiel continued to work his fingers into the young boy, he
kissed his shoulder, working up to his neck, then pressing delicate kissing
around his ear and whispered “continue, Mr. Winchester”. Dean could barely open
his eyes let alone focus on what he was doing; somehow he managed to finish the
problem and was rewarded with a slow press to his prostate as Mr. Novak added
another finger, “excellent Dean, good boys will be rewarded, and you have been
so very good”; Dean whimpered and tried to press back onto the fingers every
time they withdrew. Castiel added a third and Dean pressed firmly back every
time. Kissing and nipping the Dean’s shoulder, Castiel stopped moving his hand,
Dean continued to moan without even noticing he was doing all the work, “you’re
such a good student, and such a good little whore, I don’t even need to do
anything, you’d just fuck yourself on anything I gave you, wouldn’t you?” Dean
whimpered in reply, completely enraptured by the pressure of Castiel’s thin
fingers. The older man to milk the boy’s prostate, he began to pepper kisses
and nips along the boy’s back and down to his ass. As he reached the dip of his
back, he bit especially hard and ran his tongue over the mark, while smoothing
his hands over the swell of Dean’s ass.

   “Do you know how many times I’ve fantasized about this exemplary ass? How
many times I’ve come in my hand just from the thought?” Castiel spoke
reverently, holding the globes of his ass in both hands, squeezing and testing
the limits of their firmness. Dean quickly became pliant to his teacher’s
nimble fingers. “Please sir-“, Dean was cut off again by a violent slap. “You
never could keep your mouth shut, just as well you can’t wait, but don’t worry,
pet, I’m here to take care of you.” Castiel’s hands spread Dean’s ass while he
tentatively licked the tense ring of muscles, gently pushing in. His student
became lax, breathing out a sigh of pleasure as his teacher was nearing his
prostate.

   Pulling out quickly, “I think, first you need to work for that reward, pet.”
Castiel stood behind the young boy, running his hands over the broad chest,
flicking his erect nipples in his wake. Dean lean his head against Castiel’s
still-clothed collarbone, exposing his neck to Castiel’s mouth. The older man
nibbled at his neck, biting just enough to be almost uncomfortable then
rectifying it by sucking marks over the bite, leaving delicate bruises as his
hands explore the hills and valleys of Dean’s abdomen. Dean’s breath caught as
Castiel’s hands got closer to his throbbing cock; “look at you, pet, you’re all
wet, wet for me, aren’t you, Mr. Winchester?” Dean’s ‘yes’ was enveloped by a
moan as Castiel’s deft fingers moved over his aching dick. “Tell me what you
want,” Castiel whispered hotly. “I want- I want to suck your cock” Dean moaned.
Castiel smiled at the eagerness in Dean’s voice and stepped away from the teen
as he began unbuttoning his white shirt, when Dean looked at him pleadingly.
“You may speak.” “Can I… Can I undress you, sir?”

   Castiel smirked and dropped his hand, letting the boy begin his work. With
every button that was opened, Dean sucked a gentle mark, matching the ones on
his own neck. Castiel held in his moans, not wanting to indulge the teen. When
Dean was done with his teacher’s shirt, the trousers came off rather quickly,
with Castiel’s erection almost pushing out of them, though still trapped in his
boxers. Dean nuzzled the package through the fabric, breathing hotly over the
heated skin, trying to drag out his own anticipation. Finally he couldn't bare
it any longer and pulled the boxers down, allowing Castiel a moment to step out
of them, mouth watering from the amazing dick in front of him. The boy looked
questioningly, waiting for the ‘ok’ to touch; Castiel loved how fervid Dean was
to please under all that bravado, and nodded granting the teen permission.

   Dean licked from the base to the head, reveling in finally being able to
taste the cock he’s been fantasizing about for weeks. Like many things Dean
would never say out loud, he loves sucking cock, and he has a special rapport
for Mr. Novak’s. The boy swirls his tongue over the head like a pornstar, and
Castiel lets out a gravelly moan. The teen smiles and takes Castiel all the way
down.  

    "You're such a good little slut, Mr. Winchester, you'll take what I give
you and still want more for your greedy mouth, I bet your tight ass is just as
greedy, waiting for my cock while you suck me off with that amazing mouth."
Castiel began fucking Dean's mouth, using it for his own pleasure while Dean
moaned around the girth of his dick. The teen's own hard on begging to be
touched, his hands unconsciously moving towards his cock; before he could even
touch himself, Castiel pulled the boy up by his hair, "you insist on testing my
patience, boy". Dean whimpered, rubbing his toned body against the lithe form
of his teacher, seeking any sort of friction.

    "Tell me, Mr. Winchester, the integral of 3x⁴ - 2x dx?" Castiel moved his
hands onto the boy's hips as he helplessly pressed against the older man. "Sir,
why  now- fuck, please... I need... -" Castiel rolled his eyes and bent
his leg, effectively giving the boy something to rub against. "Mr. Winchester,
don't you want to be an engineer? You should be able to answer a simple
integral question, engineers need to be able to work under stress, Mr.
Winchester. I don't believe I'll let you come until you answer my
basic question." Dean fervently rubbed against the older man, moaning at the
exquisite friction, "you evil son of a- nggh!" Dean wasn't above begging at
this point, but Mr. Novak was in control, and Dean was to play by his rules.  
 
    "My, my, Mr. Winchester, we went over this a few days ago, don't you
remember? Of course you weren't focusing on that, were you? I was wearing a
tight black shirt and vest with black slacks. I would have been sporting a
massive hard on while you bit and sucked on your fingers." Castiel punctuated
the last part by thrusting his thigh harder against the boy's cock and nibbling
on his ear. "Tick tok, Mr. Winchester, or else I'm just going to bend you over
this desk and make you my bitch- but you'd like that, wouldn't you? Maybe I
will anyways." Castiel was biting the words into Dean's hard nipples without
ever moving his leg from Dean's crotch.


"But, sir, I'm so close...!"
"And I'm almost ready to fuck that perfect ass of your's, you best think fast
if you want that to end in your orgasm."
 
    Continuing to rub against Castiel's thigh, Dean finally concentrated enough
to get the answer, "3x⁵/5 - x² +  C!" "Such a good boy, you're so very smart,
aren't you, pet?" Castiel hummed in content while stepping away from the boy.
Dean puled at the loss of contact, searching for the firm weight of Castiel's
body. The older man motioned to the desk, "now, Mr. Winchester, are you going
to continue to be a good boy, or am I going to have to bend you over myself?"
"I'll be a good boy," there was an ardor in his voice that Castiel found very
endearing; Dean bent over the desk, laying flat on top of the assignments he
and his classmates had just completed. Dean spread his legs wide and stuck his
ass up wantonly.
    "Oh baby, look at your poor hole, it's so tight," Castiel poured more lube
over his fingers and pushed in hard, leaving Dean gasping. "You've been such a
good boy for me, answering my questions, keeping your hands to yourself,
sucking me off with that marvelous mouth, you've worked so hard," every praise
was interspersed by a crook of Castiel's fingers, running over Dean's prostate;
Dean responding to every one with a frigid gasp. "Tell me, boy, do you want me
to fuck your ass? Do you want me to ruin you for any other man? Do you want me
to make you my bitch?" Castiel relentlessly scissored and stretched Dean's
narrow hole, leaving the boy unable to hold back his almost-yelps of pleasure.
"Yes! Fuck yes! I'm your slut, make me your bitch! God, fuck me until I can't
walk, just please -" Dean panted and shouted, knowing they were alone in the
school. Castiel smiled wickedly and slicked up his thick and heavy erection.

    Dean writhed on the desk waiting, his cock trapped between the papers and
his abdomen, when finally, finally Castiel pushed in and bottomed out in one
thrust, both men groaning at the delicious pressure of relief from weeks of
pent up angst. Castiel began a acrid rhythm, pounding into the boy's ass
without remorse, further reddening his abused ass. Dean sang a mantra of
'Cas...' into the shrewd papers of his desk. Without missing a beat, Castiel
pulled Dean's face up from the desk by his hair, "who owns you?!" "You sir!
Castiel!" The older man unremittingly hit the boy's prostate with every skin-
slapping thrust. In the throes of Dean's building pleasure, coming so close to
orgasm, but holding back, Castiel stopped, pressing his cock against the small
bundle of nerves while holding onto the boy's hair, he whispered into his ear,
"come for me, whore."

    Dean came all over the assignments, desk and himself, constricting over the
older man. Castiel reveled in the howls of bliss that ripped through Dean,
sending Castiel over the edge with him. Both men writhed against each other,
sending the defiled assignments everywhere. The boy's knees gave out while
Castiel fucked him through his orgasm, landing on the desk with a soft 'thud'.
Castiel pulled out of the spent teen and sat on the forgotten chair, panting.

Come here," Castiel motioned with his hands to his lap, this time with less
prurience. Dean turned his head to face his teacher, "really? You want me to
sit on your lap? What am I, five?" Secretly, Dean hoped he could cuddle up to
the older man, on his lap or not, in a completely badass manly way, of course.
I know you're a cuddler, so are you going to come over here or not?" Dean
sighed in contented defeat and curled into his teacher's lap, even allowing him
to rub gentle circles into his back.


"I could lose my job for this, whatever this is..."
"You could also go to jail."
"Thank you for the friendly reminder."
"I'd come visit you in jail if you did... or even if you don't... I could come
to visit..."
"I think I'd like that..."
 
 
    Both men sat in complacent silence, reveling in afterglow, when a young boy
burst through the door, surprising both the teacher and the student, sending
them in opposite directions of each other (as if that would save them from the
incriminating scene); "Dean you said you'd be twenty minutes are you -! OH
GROSS DEAN!" "SAMMY I SAID WAIT IN THE CAR!" "Oh my god my eyes! I'm going but
hurry up! GROSS!" Just as quickly as the younger boy arrived, he was gone.


"Who was -?!"
"Sammy, don't worry about him... he's my, uh, little brother, I was supposed to
pick him up... don't worry, he won't say anything."


    As they began to dress, Castiel saw the dirty assignments and sighed.
"What the hell am I supposed to do about these?! You couldn't have
aimed?!" Dean smiled, handed him a note with his phone number and gave him
a quick peck on the lips, "you can show me your cuffs sometime," and with that
he was gone, leaving Castiel with a mess to clean, and another hard
on.                  
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