Personally I don’t think that’s the schools place, after all, they wouldn’t send a letter out to all parents to inform them of a gay child in school, or one with a medical condition (at least, not without the family’s request)?
What was the reason for telling parents? Was it to tell them someone of the opposite sex was going to be in changing rooms or sleeping rooms on school trips? Or so they could explain to their children/help them manage treating a boy as a girl now for example?
I agree no one else would need to be informed if someone was gay or had a medical condition, there would be no need in those cases.