Is he crazy or is he just bord?

its this guy he always staring at me when im in the hallway , when im across from him he stairs and when im at the end of the hall he still stairs at me and when i was talking to my friend that was right next to him he still was looking at me. and he stands outside of his class room every day. but the thing is we have A days & B days at our school & he should only be there on A days. but instead he's out there every day he's been staring at me for two weeks now. what should i do.