Soon thereafter he nicks a book on human anatomy, and that evening while in the bathroom, measures the size his own genitals to the pictures in the book.
In the first scene a girl needs to use the bathroom and cannot get her pants down, and asks him for help, he says he will call a female teacher and she says something to the effect of I don't care if you see me just help me get these down before I crap my pants, he does. But then it's "too late" anyway. The female teacher has to clean her.