The Obama Administration has sent a letter mandating all public schools in the United States change their locker room, shower, and bathroom policies to allow entry to anyone, based only on how the individual identifies or expresses their gender internally, and not based upon their biological status. This mandate also extends to sports teams.
This means that any boy can enter the girls locker room or showers, so long as he claims internally to feel like a girl, or vice versa. Simply claiming that one feels like a female is now sufficient proof to allow unrestricted access to these private places where girls will be in various states of dress and undress.
You can read the full letter here.