the technical guidance to schools says that the harassment provision of the Equality Act doesn't apply to gender reassignment
I don't know why harassment only applies to certain protected characteristics here and whether that's only a school thing.
IANAL but it seems like the currently published guidance is potentially wrong on this. I guess the interim guidance (which does cover schools and has proven to be lawful) provides a reasonable hint to suggest that the logical direction of travel will be that harassment can apply to gender reassignment in all situations covered by the EA as per Forstater. We won't find out any time soon though as the final guidance that Phillipson is sitting on doesn't even cover schools.... she's got a whole extra sit-in protest opportunity after her current one finishes.
It has to be a proportionate means to achieve a legitimate aim though, I'm not sure what the legitimate aim of stopping boys wearing dresses would be?
Whatever their reason, this needs to apply to all boys (of the biological sex variety). Not just those that are covered under the PC of gender reassignment because they are proposing to undergo a process to change their gender (whatever that means... FFS). It would be interesting to know what the legitimate aim is.
Maybe schools are concerned that up skirting would be even more traumatic for everyone concerned (not just the skirt wearer) if it meant being exposed to a dangling bollock? I can't help thinking about that Alan Partridge episode where a poor distressed Lynn had to let Alan know that the boys were out of the barracks....
But, joking aside, it is difficult to imagine what legitimate reason there is for stopping a boy wearing a skirt to school. As long as he knows he's a boy, and isn't showing signs of fetishist display (perhaps that's the legitimate reason?**), surely it's difficult to justify the restriction.
**Which brings it right back round to safeguarding. Unfortunately, there will be boys who are being groomed into the world of autogynophilia. Some will want to wear a skirt to school as a direct result of this, even if they aren't consciously aware that this is what's driving their need to wear it. Sadly there are young boys (many autistic, socialising online in gaming and anime worlds, with emerging opposite-sex attraction as their sexual maturity starts to kick in) who are on this pathway. Refusing to let any boy wear a skirt because of this risk may well be legitimate. They are children, not adults, and as such are vulnerable. Maybe that particular point needs to be captured in the KCSIE?