My parents wont let me play football?

so about 5 months back my parents said they would allow me to play football for my high school. today i got all the paper work and now they keep saying they won't let me play! i have football cleats and gloves and the school provides 2 uniforms pads and practice jersey for free (only for the season) but they keep making up different excuses like i'll break my braces so i told them i'll wear a mouth guard then they said i would hurt my legs so i said the school gives out girdles and they kept saying no and i even said i would wear sports goggles to be extra safe! I want to play because my friends are all playing and i haven't played a high school sport yet.i'm already late for the football camp that is $150 so i decided to just do summer weight training for $40 but they keep saying i'll get hurt. I'm 5ft9in and about 195lbs i have pretty good endurance and i'm pretty strong and thats why the coaches say i'd be perfect to play but my parents wont listen. how can i change there minds?