So let's pick apart the question "to what extent are parents informed when a child expresses feelings of gender distress at school?"
Firstly the question is badly framed. It's not clear what's meant by "gender distress" and it could incorporate a range of scenarios, from identifying as trans and demanding social transition, to saying they don't know what their gender identity is, in a lesson about gender identity. This lack of clarity is going to make it hard for schools to answer properly.
Second the analysis of answers is poor. There are 3 categories, "reliably informed", "not reliably informed" and "insufficient details provided".
It is impossible from these answers to establish how many schools aren't informing parents, which is key to the whole argument the paper is trying to make. I don't know why they haven't include a "not informed" category but its a bit suspicious.
The definition of "reliable" is very important to the interpretation of the answer. If "not reliable" means not in all circumstances, that's a different interpretation to if "not reliable" means "our records don't tell us in every case" or "we didn't informed in a certain timescale".
Because the findings are so poorly constructed its impossible for me to say whether I agree or not.
I also feel its indicative of a priori research, e.g. the researcher decided what they wanted the answer to be and made the evidence fit that. That's very bad practice, but in line with bodies producing "research" to meet a certain agenda.
And just to follow RTB with a flex about my credentials I have a PhD and published papers, so am very familiar with critiquing peoples research.