Yeah, this is what gets me. Some parents are shitty, and I can see the issues with this as it's not unheard of for kids to be kicked out by homophobic parents after being outed, etc
But in the flip side, parents are legally responsible for their kids try increasingly cut off from the information that might be important for caring for those kids. They can ask a doctor to not disclose drug use, and apparently now a teacher not to disclose their gender identity decisions, leaving the parent might be clueless up to the point where it grows into a major issue and blindsides them.
Life isn't an episode of Leave It To Beaver. Not all kids have daily sit-downs with their parents where they discuss in detail everything about their lives. At a certain point, a lot of kids often start cutting out their parents thinking that it's part of establishing their own independence, and sometimes -especially with issues of sexuality/etc - they may be embarrassed to bring those forward to their parents.
Do parents have a right to know everything about their kids lives? Maybe not. Parents DO have a responsibility towards help educate their kids, help them navigate life and deal with major life changes and decisions. Educators have historically had a duty to keep parents informed of major developments in school which might affect their children or - if they have evidence the child is at-risk - to report cases of abuse to the appropriate authorities.
It's a tightrope, for sure, but expecting parents to do their job while potentially withholding vital information is not a good look either, and a lot of decisions from government (on both sides) lately are starting to have a "it's for the children" authoritarian feel.
I would support my kids regardless of how they choose to identify, their sexual orientation, etc, but when stuff is happening in regards to that I would damn well want to KNOW so that I can support them properly (possibly including learning more myself)