Tell them 당신 really want to play and show them that 당신 know how to play. Keep fighting until they let 당신 play football. If 당신 take no as the final answer they won't take 당신 seriously for any other sport 당신 might want to play. In my school, there is a girl on our football team and none of her teammates treat her differently. Teams from other schools have a lot of respect for her.