An erection.

Suddenly, something happened, my cock twitched. "Oh god no!" I thought to myself. Standing naked in front of half a dozen girls, is messing with my body and mind. My body loves the thrill, the excitement and wants to take things a step further, but my mind is battling with it, trying to see reason reason. Just then, it happened, my cock stood up in broad daylight and in front of everyone.

A collective gasp from the students and the teacher filled the room at the sight of my arousal. Some girls giggled to themselves, some covered their faces in embarrassment and the rest just sat with their jaws on their desks.

"He's got a boner." A 5'5 girl with brunette, curly, shoulder length hair, blurted out.

"The correct term is erection, Jane, but yes it does appear James is aroused." Miss Hallcroft corrected. "Does anyone know why the penis stands up like that?" Miss asked, addressing the class.

Everyone shrugged or shook their heads.

"During sexual arousal nerve messages egin to stimulate the penis. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the copora cavernosa, making the penis expand and creating an erection." Miss explained as she pulled up a PowerPoint with diagrams, showing the inner workings of the penis. "

"Why is he aroused?" Another girl asked, who was sitting at the back.

"Something to note is: just because the penis is aroused, doesn't mean the guy the guy is thinking of anything sexual. On average, a guy will have 11 separate erections in a day and the person won't even be aware of most of them. What has most likely happened, Cindy, is that James is nervous and his body has reacted like this." Miss answered in rather calm manner.

"Miss?" Another girl asked, raising her hand.

"Yes, Claire." Miss responded.

"Can we see him cum?" Claire asked.