"OK, first you need to find a partner," the teacher says. You look around and see boyfriends and girlfriends are generally partnering up, and you go up to Mina, a girl you don't know too well, and ask her.
"Alright," she says casually, and the two of you sit on a mat together, waiting for everyone to get partnered up.
Once everyone has, the teacher gives the next instruction. "Now, you all need to undress. Get comfortable seeing each other's bodies, because understanding them is a crucial part of healthy sex."
To your surprise, Mina pulls off her top pretty quickly, while you fumble with yours, and she smiles as she sees you trying to hide your hard-on. "You don't have to hide that, you know," she says, kindly but a bit insistently. Nodding, you pull your shorts off, and she looks enamored at your hard cock as she removes her skirt and panties, standing naked in front of you.
"There's two easy ways to try what we're doing first, which is PIV sex, or penis-in-vagina sex," the teacher explains. "Depending which is most comfortable to you, you can try missionary position, where the girl lies down and the boy thrusts into the vagina; or cowgirl position, where the boy lies down and the girl rides the penis. You might want to switch positions partway through, depending on what you find comfortable, which is fine. But make sure your partner is comfortable with it before doing anything."
Turning to you, Mina asks, "Which do you wanna do?"
"Um, the first one?" you ask. "If you're OK with that, I mean."
"Yeah, that sounds good," she smiles, and lies back, spreading her legs. You get atop her, and rub your cock along her slit carefully. Pushing it inside her slowly, she gasps, and her hands cling to your arms tightly.
"Oh, I almost forgot to mention something!" the teacher points out. "When a girl is first penetrated, the vagina has to stretch to accommodate the penis's girth. So boys, make sure to thrust slowly, and only move once the girl is comfortable with you doing so. It can also help to play with the breasts or clitoris to get the girl more aroused."
Looking down at Mina, you ask, "Should I try that?"
She nods. "Play with my tits a bit." You do as she asks, and she moans a little as you cup them and rub her nipples. You feel her moisten around you, her warm, tight shaft feeling so good.
A few moments later, you pant, "I really wanna move."
"I think it's OK now," Mina replies, and you feel an intense wave of relief as you start thrusting rhythmically, both of you groaning eagerly as your bodies slap together and you feel pleasure coursing through you.
Your thrusting grows faster, and you feel her hands grab for yours, holding hers as you continue thrusting eagerly.
"I should say something before any of you can cum," you hear the teacher say, but you're too fixated on fucking Mina to pay attention. You make out something about how you'll have to do one thing if you cum inside and another if you remembered to use a condom or you pull out, but you don't know exactly what. You'll find out once you cum, whichever way you do...