In class I sit behind this girl who is always turning around and looking at me but at as soon as we get out the class room and we are close she doesn't even look at me why?

It sounds like she might be shy or unsure about approaching you outside of class. Turning around in class could indicate curiOSity or interest, but once outside, the social dynamics change and she might feel more nervous. It could also be that she’s trying to gauge your interest before making any moves. If you're interested, maybe try initiating a conversation to see how she responds!