Fine, until halfway-through

The class was Biology, and to make matters worse, they were discussing reproductive systems and sexual relations between mammals. Annabelle uncomfortably shifted on her seat, her discomfort created by both her panties and how aroused she was getting from the class. The teacher, Miss Estelle, luckily did not notice, nor did the other students, and she managed to take whatever notes she needed to take from the explanations in the class.

Everything seemed to be going fine, and Anabelle was sure she would make it through the class, and hopefully the rest of the day until she went to meet Maura at the coffee shop. However, just as the class reached the midway point, Miss Estelle turned to the class, a serious but slightly amused look on her face.

"Alright, class, we all know there is a limit to how much simply explaining things can teach you. As such, I have gotten in contact with the Health Board, and I have been allowed to carry out a live example of mammal reproduction with two students of my choosing. For this example I have chosen Annabelle and Greg for this. Please, the two of you, get up and come to the front", she explained, and Annabelle gulped. Miss Estelle has used very scientific wording, but she knew exactly what she meant.

Quite nervously and aroused by the prospect of what was going on, Annabelle got up and headed to the front of the class, followed by Greg, a jock known for having a large dick. They both knew better than make Miss Estelle angry, as she had a lot of influence in the school. Annabelle was a bit confused as to why she would choose to do this, but decided not to question it.

As soon as they both were in the front of the class, Miss Estelle ordered them both to strip, which they reluctantly did. At least Annabelle and everyone else in the class did get confirmation about the rumors about Greg's size, which was fairly large, even now that it wasn't fully erect.

"Looks like our example needs a little help to get fully hard. Want to help, Annabelle? I believe you know what you have to do", Miss Estelle said, and Annabelle nodded. She knew the perfect way to get Greg nice and hard for the live example Miss Estelle wanted.

She quickly dropped to her knees, taking his dick in her hands and began to suck him off with the skills she had earned over the last few days. Greg groaned in pleasure as Annabelle did her best to get him hard, as the faster she did it, the faster the slightly embarrassing situation would be over. She continued to suck him off for a while, feeling his dick become harder and bigger inside of her mouth, but stopped when she felt he was close to the edge, as Miss Estelle wanted some proper fucking for her example. Greg was clearly disappointed when she moved away and got up, but that was replaced with lust when she bent over Miss Estelle's desk, showing him her ass and soaking wet pussy.

He quickly got behind her and rammed straight into her awaiting pussy. She wished she had been able to take the load in her mouth or all over her face, but it didn't really matter now, especially as slutty moans left her lips while Greg thrust into her. Miss Estelle seemed pleased with the demonstration of human sex, telling all the remaining students to stop jacking off or recording it and take notes on the act.

Greg continues fucking Annabelle for fifteen minutes before he comes, filling her with his cum. After his done, a flustered and panting Annabelle quickly recovers her clothes and puts them on, despite having Greg's cum leaking from her. It feel uncomfortable, but she continues to what she was told to do by Maura, deciding it is only a minor annoyance. The class soon returns to normal, except for some murmuring and a few people masturbating while Miss Estelle is distracted.

As soon as the class is over, Annabelle rushed to her next class, which thankfully came and went uneventfully, while the discomfort from the cum and her panties begins to slowly fade.