If you're aware of children talking among themselves to reaffirm and support a child in starving themselves and hiding their food intake from their families would you feel that was none of your business either? Children talking amongst themselves and affirming and encouraging a child sending inappropriate pictures of themselves to another child or adult would you feel that was none of your business?
It's a very difficult line to walk, but supporting transition is not a neutral act, it is a potentially serious safeguarding one, particularly when it is happening without medical guidance and parental knowledge and consent.
The main issue to begin with is that some adults see any response but affirmation as the safeguarding disaster - as they have been trained to do by the political lobby. Therefore there will be a lot of 'but this is harmless and it's unkind/unfair to stop them' that really believes underneath that adults who have concerns are actually abusive and wrong.
This will take a long time to turn around and I suspect that yes, it will have to involve law to make teachers step back behind the line of professional duty of care and objectivity. And I suspect Prevent are going to need to help, because this is programming. This is a trained system to make caring adults believe that caring means transitioning and resisting adults who do not see things as they do, while seeing them as at best uneducated and uninformed, and at worst as a direct threat to the child.