@AmaryllisNightAndDay ”case by case” means the same issue might have a different solution in different circumstances, with different resources, at different ages. You might have a legitimate aim, but in a particular circumstance, a solution which works in a large school might not be proportionate in another.
The EqA does allow single sex provision, other acts and guidance insist on it. That does not mean transgender people are excluded - they can be under certain circumstances defined in the Act (see AEA vs EHRC and statutory guidance).
I appears you are arguing for forced social detransition here - I hope that’s not the case.