I can see how people raised in stable loving families think 'why shouldnt the parents know?' But I was raised by a raging narcissist, if dad slept bad a head-punch during breakfast was not uncommon. First memory I have is being hurt by my dad...
If I were trans this would have sealed my fate; killed via 'exorcism'
If the kid doesnt want their parents to know about their gender identity well that isnt a bad kid, those are bad parents. Yes really.
Believe you me, the good parents dont need the school to tell them, they already know because a child that feels safe will just tell you. If you really love them you will already know anyways just from paying attention to them.
I know people with mental diagnosis who support this shit. Try explaining to them that they are one the list of undesirables too, or dont if you value your time and sanity.