This discussion should not be focused on simply toilet logistics. The accommodations for locker rooms do pose tremendous challenges economically to schools if any molecule of privacy is to be retained between the genders.
The real question is neither bathrooms nor locker rooms, it is the real distinctions between the sexes. Sorry to be pedantic but people do not have genders, words do. People have a biological sex. For the last hundred years, with the birth of the Feminist movement, there has been a determined effort to deny the real differences between the sexes and the roles they play in both the family and in society. The use of the term "gender" rather than "sex" is a part of this effort to say that "gender identity" is merely a social construct that has no relation to one's biological sex. This really started to gain ground with the Sexual Revolution and Women's "Emancipation". The present push for the recognition of "Transgenderism" is just the end game to force everyone to accept this ideology.