Does this sound illegal to you?

my school has a strict open enrollment policy, where they except kids outside of the district we barely live out of the school district now, and we filed for open enerollment. many people said it was a first come first serve policy and my mom made sure to get there the day open enrollment was being excepted and one of the very first ones there. my two brothers got in and one thee two largest grades in our school. mine is the smallest and i did not get in. i have chrohns disease which makes me very sick, and with doctors appts. and just being sick i miss alot of school. so i dont believe they have been quite honest with us for the reason why i cant get in. now my aunt (who is a doctor) said it is illegal for a school or anything however to not except you because you are sick. does this sound right ? what would you do?