I'll never forget the time a male friend, when we were both in our early 20s, said that the reason he and his friends didn't do as well as they might have in GCSEs was that they spent pretty much every waking moment of their mid teens trying to figure out schemes to get into the girls changing rooms.
What a good idea to enshrine in law to make it easy peasy to do. No need to transition, just describe yourself as gender fluid and you can be one of the lads 90% of the time except on Wednesday afternoons for sports lessons.
This really isn't about the tiny number of pupils with gender dysphoria. There are far far more straight "cis" males who will take advantage of these guidelines than there are dysphoric kids who might benefit from them.