Human Sexuality Class - Demo

She was fully aware that she could be used for "practical demonstrations" when she signed up as the model for a human sexuality class. She didn't expect to be getting so excited about it though...

***

I nervously pushed open the door of the classroom and peered inside. I had been told to arrive five minutes early and the classroom was empty except for the lecturer. "Come in, come in!" he said upon spotting me hovering apprehensively in the doorway.

I entered and approached his desk. "Great, lovely to meet you," he said, "Just need you to fill in the liability waiver here," he indicated a form on the desk. "Just the standard agreement. You'll get paid at the end of the class. And... you are aware that this is a practical demonstration and you will be fully naked?"

"Yes... of course," I stammered, picking up a pen and scanning the document. I was quite used to being naked in life classes for the art facility, but this was my first time as a model in the biology department.

I noticed that the room wasn't quite as empty as I had first thought. Sitting quietly in a chair next to the blackboard was a boy. He was kind of cute, with quite long curly hair. He glanced at me uneasily, but didn't seem to want to make eye contact. "This is George, the male model for the demonstration," the professor said. "Take a seat next to him please."

I went and sat in the adjacent chair. His hands were clasped on his lap, and he was entwining his fingers nervously. I recognised him as a fellow third year student, although I hadn't spoken to him before. "First time too?" I asked him, trying to make conversation, but just then the door burst open and a number of noisy students rushed in, chatting and joking with each other. The room soon filled up, and they all took their seats facing the front in individual seats with the little built in desks.

Once the room was full, the professor began the lesson. I pretty much tuned out to what he was saying and scanned the students sitting facing us. They were first years, so I didn't know any of them thankfully. A mixture of boys and girls, most of the boys kept glancing at me and smirking. After about five minutes I was suddenly aware that the professor was introducing the two of us models and asked us to come and stand at the front.

"If you can both remove your clothes please," he said. I have to admit, I do get a slight thrill being naked in front of the art classes I have modelled in. I like the feeling of all their eyes on my body and I expected this to be no different. I pulled my sweater over my head and then my vest top. I unbuttoned my jeans and slipped them down to the floor, pulling off each leg in turn until I was just in the simple white underwear I had chosen.

Next to me, George was also down to his Calvin Klein underpants. I glanced over as he pulled them down and almost gasped out loud. His cock, although soft, was massive, both thick in girth and very long. It hung down limply between his legs, framed by a thick patch of hair that also extended up his belly and chest.

I hastily turned my eyes back to the class and unhooked my bra, exposing my small, firm breasts. Then I removed my final item of clothing, slipping down my knickers and revealing my own trimmed bush to the watching eyes. Some of the students looked embarrassed, red in the face, but others looked excited. One boy right at the front was giving me a big grin with a twinkle in his eye.

George and I stood there, upright and completely naked, as the professor walked back and forth in front of us, talking about various parts of anatomy and pointing at them his telescopic pointer. "Here we see," he was saying, "the female nipples are not yet aroused. The areola are widened and flat and the nipples themselves are not yet hard." The end of the pointer hovered an inch from one of my nipples.

"And below," he continued, moving the pointer to indicate the area between my legs, "the vulva. Not to be confused with the vagina, of course, which is the interior part we can't see at the moment. In this subject you can see that she has chosen only to trim and not remove her pubic hair."

I was enjoying them all looking at me naked. Especially the boy in the front with the twinkling eyes. I felt myself getting a bit aroused and my heart was thumping in my chest.

The professor moved on to George, pointing out his much smaller nipples and then his penis and testicles. I glanced over again as the professor explained that he was uncircumcised. He made no mention of the fact that George's cock was freakishly big.

"Okay," he said, striding back in front of me. "Sabrina, if you could lie on the desk please. Yes, like that, lift your legs up." I led on the desk, my feet facing the students. Under his direction, I opened my legs up and put my feet on the desk. Fuck, they could all see my opening now. I felt a further thrill at the thought, but I couldn't see them as I was looking up at the ceiling.

The professor began indicating parts of my vulva with his pointer. "This outer area here is the labia majora," he was saying. The cold metal of the pointer touched me, and I felt him part my lips slightly with it. "The vaginal opening, and above the labia minora. This subject has fairly small labia minora but it's not uncommon for them to be much bigger and extend beyond the labia majora."

The pointer kept gently touching me. My heart was racing now and I felt my vagina getting wet. I hoped it wouldn't be visible. "This is the urethral opening where urine is excreted from and also female ejaculate, we'll be covering that in week five. And finally, the clitoris. Boys take careful note exactly where that is," he joked as the pointer came to rest on my clitoris, nestled under its hood. The class tittered dutifully.

"Thank you Sabrina, you can stand up again," he told me. We stood naked and motionless before the class again as he continued to drone on about arousal.

Eventually he indicated to me again, "Now, remember how we saw that the subject was not showing any signs of arousal?" There were a few half hearted nods from the class. "George, can you rub or suck Sabrina's nipples please and we'll see if we can stimulate them."

George made eye contact with me nervously and then approached. He lifted one hand up to my breast and cupped it gently, then very carefully he rubbed my nipple with his thumb. It felt nice, and a burst of pleasure ran through me. The professor was getting excited now, "Look!" he declared, "as we expect, the areola has tightened and contracted and the nipple has hardened as blood has rushed into it."

I was enjoying the stimulation quite a lot and my breathing was getting deeper. "See how the subject's breathing has also changed," said the professor, "George, give the other one a suck, see how much you can stimulate it."

George bent down and took my other nipple into his mouth. His tongue was wet and warm and it explored my nipple. "Suck it please, not just lick it." said the professor, not happy with George's technique. He started sucking more effectively, pleasure flowing through my body. I let out an involuntary gasp, which seemed to please the professor no end as he gestured excitedly to the class.

"Okay, that's enough," he said. George returned to his position beside me. The professor indicated my nipple with the pointer, and flicked it back and forth with the end, making me gasp again. "Look, it's very hard and so much larger now. That's the result of the extra stimulation we saw."

"There are other signs of arousal we can look at on the female in a moment," he told the class, moving on, "But first let's have a look at arousal on the male. Who can tell me the most obvious signs of arousal in the male of the species?"

There was a slight hesitation in the class, and then a girl in the middle row wearing a beanie cautiously put up her hand. "Erection?" she asked.

"Exactly!" said the professor. "All the same signs as we saw in the female are possible of course, increased heart rate, change in breathing, even hardened nipples, but the most obvious sign will be the erection."

Turning to me, he said, "Sabrina, can you get on your knees and stimulate George's penis with your mouth please." My heart missed a beat and then started racing. The thought of sucking George's huge cock in front of the whole class sent a bolt of lightning to my cunt.

The professor reached behind the desk and handed me a cushion. I put it on the floor in front of George and knelt on it. His cock was inches from my face. It was still soft, but so long. I gingerly reached up and held it, my hand only just reached all the way round his girth. I felt it twitch in my hand. I wrapped my other hand around it too, and that still left a couple of inches, which I put in my mouth.

Now it was George's turn to start breathing heavily as my tongue played with the head of his cock. I could feel it pulsing and swelling in my hands and mouth, thickening and hardening. I bobbed my head back and forth, only getting a couple of inches in my mouth, but using my hands to wank his shaft too.

The class was absolutely silent and they watched in rapt attention as I sucked him and he got harder and bigger. I could feel their stares on us. I was getting such a thrill doing this in front of so many people, and my cunt was now soaking wet and aching with desire.

I took his cock out of my mouth and looked up at it, still holding it in both hands. It was fully erect now in all its magnificence and wet with my saliva.

"Perfect!" said the professor, "And quite an impressive specimen as you can see. Notice how the veins in the penis have become more prominent and also how the scrotum has become tense and doesn't hang down so low."

I looked out at the class, all of them watching us breathlessly. Some of them looked flushed and uncomfortable, others looked excited. From my position on my knees I could see under the desks. All of the boys had large bulges in their trousers. Fuck, there were fifteen other hard cocks out there, the thought made me even more turned on. The girl in the beanie had her legs crossed and was squeezing her thighs together, I knew what that meant. There was a blonde girl in the front row sitting with her legs wide open. I could see her light blue panties had a darker wet area on the front.

"Thank you Sabrina, I think you can let go now." he said, causing a ripple of nervous laughter around the class and lightening the tension. I stood up and resumed my position, wiping my wet mouth with the back of my hand. George turned back to face the front, his big cock still pointing straight upwards.

"Now, I mentioned there were other signs of female arousal. Let's see if any have presented themselves. Sabrina, if you could turn around and bend over the desk for us please." I did as he asked. "And if you could kindly spread yourself with your hands, thank you, that's perfect."

I was bent over the desk now, my hands on my cheeks and spreading my cunt wide open. I was aware that the whole class could see my asshole and my open vagina. I felt the telescopic pointer against my ass. "So, who can tell me what signs of arousal we can see here?" the professor asked the class.

I couldn't see who was talking, but a boy cleared his throat and spoke up, "She's wet professor," he said.

"Good," said the professor, "The vagina has produced some fluid to aid in lubrication, and you can see it's practically dripping out in this case. The act of stimulating her partner has clearly caused her to become quite aroused. Anything else?"

There was silence from the class. "Come on," he encouraged.

After a few more moments, a nervous female voice said "Labia are engorged?"

"Yes! You can see that is quite obvious here," the pointer touched my lips. "In fact, the whole vulva is slightly swollen and engorged with blood now. Her clitoris also looks a lot bigger and redder now." I just stood there, bent over the desk, my nipples pressed against the cool wood as everyone stared at my cunt.

"Right!" He said, "On to the next part of the demonstration. Sabrina, can you come round the side of the desk please, yes bend over the desk again. That's right, so they can see you from the side. And George, you come behind her and penetrate her." Fuck, my heart started racing again. He was going to fuck me in front of everyone? I desperately wanted him to fuck me, my cunt was aching for him, but in front of the class?

I felt George approach me from behind, and then his cock pressed against my opening. He positioned it inside my folds and slid inside me on one movement. Deep inside me. I cried out as he stretched me open and filled me. Pleasure rushed through my body and I felt every part of me tingling with energy.

I was bent over the desk, my head turned to the class. I could see their faces watching me as George thrust inside me, my cunt gripped him tightly. The boy with the nice eyes in the front row was still grinning at me hungrily. I could see his hand was on the bulge of his trousers under the desk. A few of the girls had their hands over their mouths in shock, but most of them were looking on with a longing interest. Beanie Girl in the second row also looked like she had one hand under the desk.

George was fucking me quite hard and roughly. He had one hand on my ass, spreading my cheeks so he could see my asshole and lips gripping him. His other hand was on my back, holding me down onto the hard desk as he pounded me with his cock. I'd never been fucked like this before, and I was letting out a loud cry with every thrust.

The professor was pacing up and down, still talking to the class, occasionally gesturing towards us as he explained something. I couldn't understand what he was saying, my whole attention was taken up by the relentless pleasure in my core as George fucked me. I felt a climax rising inside me, which made me slightly anxious; I felt it would be embarrassing to lose control and orgasm in front of the class.

Suddenly, the professor said, "Stop right there then George, that's great." George pulled out, and I glanced round. He held his hard cock in one hand and it was covered in my essence. I felt empty and open, as if something I needed had been taken away from me and left me incomplete. The professor was pointing out the creamy wetness on George's cock.

"Okay, I think it would be interesting to demonstrate a couple of other key sexual positions." he continued. "Sabrina, would you mind getting on your back on the desk and we can demonstrate the missionary position."

I lay on the hard desk, and the professor passed me the cushion to put under my head. Luckily, it was a sturdy, old fashioned oak desk, and it hardly moved as George added his weight to it, climbing on top of me between my legs.

"Now, we saw in the previous position that the penis can stimulate the g-spot, but the clitoris would need manual stimulation. In the missionary position however, the male's pubic bone can provide some clitoral stimulation." He then continued to say something about it being the most common position, but at that point, George's huge cock entered me and I completely switched off.

Our gaze locked together, George began to fuck me hard again. I loved the feeling of him inside me, fucking me as deep as he could go. I felt my climax rising again.

"George, please. Can we demonstrate some kissing, let's try to make it slightly realistic for the class." the professor told him, before going back to talking to the class about how the vaginal canal lengthened during arousal.

George lent over, and his tongue was in mouth. He was warm, and tasted of mint. His curly hair hung down over my face. The combined sensation of the passionate kiss with hard thrusting into my core suddenly spiralled me out of control and I felt myself go over the edge of the precipice. An intense orgasm washed over me, consuming my whole body. I screamed and dug my fingers into George's back as I rode wave after wave of pleasure that coursed through me.

George slowed, and kissed me again as I came down from my high. The professor was continuing to talk to the class, "So, we weren't going to do the female orgasm until week three, but never mind. As our subjects have accidentally demonstrated already, it's interesting to note that only around 25% of females can climax from penetration alone."

He was slowly moving his cock in and out of my soaking cunt now, giving me a break after my orgasm, but it felt amazing. I was already hoping that I'd be able to meet up with him privately for a more intimate sex session. And he was a great kisser.

"Fantastic," said the professor, "But we're running out of time, so let's move on to the male orgasm." He fetched a chair and placed it in front of the class. "George, if you could sit on the chair please. And Sabrina, if you mount him. Let's make sure everyone can see properly."

I walked over to where George was sitting on the chair. My legs were weak and shaking from the orgasm. I could feel my juices running out of my cunt and down my leg and I was covered in sweat. Looking out at the class, Nice Eyes was clearly wanking under the desk now, as was Beanie Girl behind him. The rest of them were squirming in their seats looking hot and bothered.

I turned my back on the class and straddled George, sinking down onto his cock, feeling him filling me once again. The professor was behind me pointing out the details of the penetration and how my lips gripped his penis. He also pointed to my exposed asshole, "We'll cover anal sex in week four," he told the class.

I started to ride George, wrapping my arms around him as I rode him on the chair. I wanted the sensations to last forever. The thought of thirty pairs of eyes watching my lips wrapped around his cock only spurred me on even more. I started fucking George as hard as I could, leaning in to thrust my tongue in his mouth.

"Okay George, when you're ready you can climax inside her." the professor said, folding his arms and stepping back slightly to allow the class a good view. George's hands grabbed my ass and he spread my ass with his fingers as I rode him. I felt myself coming again. I cried out as my whole body shook and my cunt contracted on his cock. His fingers gripped my ass tightly, and he let out a low groan as I felt him unload his cum inside me, his cock throbbing and pulsing.

We held each other tightly as my orgasm washed over me, and his cum filled me. I grabbed his face in my hands and kissed him sensually. Even the professor was momentarily speechless. There was not a sound from anyone in the class.

Finally, I lifted myself off his cock and floods of cum poured out of me, covering George's cock and running down his legs to the floor. We were in quite a state, covered in sweat and cum.

The professor regained his composure, "An excellent demonstration from our two models," he began, "Please give them a round of applause." There was a half-hearted smattering of clapping from the class.

The professor continued, "The semen in this position is leaking out of the female. If they were having sex for breeding purposes, the missionary position would be better."

The bell for the end of the lesson rang and he raised his voice over the sounds of the rest of the class getting to their feet and packing up their things. "The homework for this week, please try to engage in the sexual act yourself with as many partners as possible, I'd like two thousand words on your experiences, due in before the lesson next week."

The class filed out and George and I retrieved our clothes and hastily got dressed. The professor paid us both twenty pounds each. "Not too bad for a first attempt," he said, "Same time next week." And with that he left the classroom.