Mansplained

There is this guy at my school who always acts like he knows more then me. Everytime I talk about anything remotely intelligent he tries to talk over me and re explain the subject even though I have already explained the exact same thing. He once tried to explain to me how female genetalia works because of course, why would I, a female know about my own body. Keep in mind this boy is almost dropping out of school and I have a 95% average. When i talk to him i feel like he is talking down to me and not to me. At the same time i dont want to make a big deal out of it because i dont want to seem crazy.