My son was injured during gym class. The school says their insurance doesn't cover this but could they still be held liable?

My son was injured by getting tangled up with another kid while playing flag football. He was knocked out for a few seconds and needed 5 stitches in his upper lip. He also fractured the root of his front tooth. The woman who handles insurance claims said that this is not covered. It seems to me that they are liable because this is something he is required to play and he was in their care and on their property. I have paid quite a bit in deductibles and lost a day of pay because I run a housecleaning business and when I don't work I don't get paid. - Is this your question? Add additional information