how do i get sick or avoid a week long unskipable event?

i have this event coming up that is required to go to if you audition (which is mandatory) and pass. i have begged my teacher multiple times to not let me go this year because of how it terribly affects my mental health every single year because of many reasons. im already getting professional help and i literally have a 504 but still no way around it. i literally have no choice but to do it unless i get extremely sick to the point where i cant show up to school. ive literally tried to miss it before because i was sick and my medication at the time was giving me medical complications like stiffness and she still forced me out of class ( it was the end of the day) after saying i was sick. im actually going to lose my mind what do i do??