There is no Constitutional right to force one gender to compete against another gender. The rights of a transgender female to compete against biological girls in physical sport, does not outweigh the fairness and physical safety of the entire girls' team.
Why is this being questioned? I have absolutely nothing against someone who is transgender, but no group regardless of gender, race, sexual orientation, etc., should have rights above and beyond others. Letting transgenders play sports on girls teams isn't giving someone rights it's taking away the rights of others.
By the way, they can compete with the boys as there are no rules against it. So they're not being told they can't play sports in public schools. This is a lie. How unusual!