Does a school have the right not to let me in?

5th year i had bad attendance due to bereavement, depression and anxiety. so there not letting me sit exams, and now i there not letting me into 6th year, its a new school because my old one is shutting in the summer, but does a school have the right not to let me into 6th year? im not bad behaved and im really bright and quick at getting work done and keeping focused. i need help because all i want to do is go to this school and get an education.