I haven’t checked, but isn’t it the GRA 2005 which restricts the awarding of a Gender Recognition Certificate to over 18s?
If applying for a GRC is/used to be a two year process, then the implication of that would be that 16yos could start on “a process of” reassignment and start changing “other attributes of sex”. Given that the legislation mentions “physiological” attributes separately, the “other attributes” must refer to non-physiological attributes - ie clothing, name, pronouns, stereotypical behaviour, stereotypical hobbies and interests.
Feminists would, of course, argue that regarding various sexist stereotypes as “attributes of sex” is i) utter nonsense ii) sexist drivel which perpetuates inequality iii) the depressingly predictable product of a male dominated political party system and male dominated legislature iv) even more depressingly getting worse as a result of vociferous campaigning by Stonewall, Mermaids, Press for Change.
I can see how the lawyers have reached a view that banning social transition for over 16s could be subject to legal challenge.
That doesn’t stop the UK Government on issuing clear advice to schools that:
social transitioning is not a neutral act,
social transitioning risks putting young people on that pathway leads to significant, life changing physical interventions,
there are increasing numbers of young people regretting the loss of the fertility and the significant and irreversible physical harm done to them by going through this process,
the claims of suicide risks by certain lobby groups/commercial provider as part of their campaign to press for social transitioning and hormone treatment are unevidenced,
the emerging evidence is that cross sex hormones can exacerbate mental health issues.
The guidance could also state that - in the context of legal action against the NHS - the government understands that, whilst X teachers union is in favour of social transitioning of school children, individual headteachers, teachers, and school governors may have concerns about the potential risk of future legal action against them on the grounds of them having actively encouraged young people towards, or failed to protect young people from, this life-changing course of action. The purpose of this guidance is to support schools in keeping school children safe from harm and advises the following: etc.