While I support the people in the LGBTQ community, there are a couple issues which need to be addressed. One is restrooms and locker facilities. Sharing facilities with transgender people invites potential risk (woman in a male body) on the other girls - and especially vise versa. For a boy who was a girl, picturing the reaction of the boys towards that person changing in the locker room would expose students to a woman’s body a lot sooner, and there are boys who would find a way to act on those feelings. So shared facilities leads to increased sexual exposure to students, uncomfortably for (I hesitate to say, but) normal students, and the potential for rape and increased bullying.

Next is gender the gender specific activities. Men and woman are biologically different, and even with hormonal therapy and surgical changes, a trans person will still be different. There are already examples of trans women competing with woman-at-birth and blowing them out of the water. Even the Olympics has a current one year mandatory therapy period before trans people can compete, but they are considering extending that because women who were men at birth are still out performing women. Allowing transgender students to compete in the gender they identify as would either make it more difficult for the students or overly easy for the students. 

Those are the two biggest issues that I believe would need to be addressed so that activities are fair for all the involved students, and general education, like gym, doesn’t provide more opportunities for discomfort, bullying, and rape.