Why do they give me dirty looks and laugh? ?

ill walk past a group or girls and some guys that are 2 or 3 years older than me (in highschool) with a few of my friends. theyll all stare at me, even when im a bit down the hall. then the girls will give me dirty looks when i walk past and laugh too. it makes me feel really bad about myself, and im even a bit scared to walk past them. im not ugly, i model and have a good body. why do they do that?