The timeline for this needs investigation.
How long have children being able to identify themselves into single sex facilities in schools?
If this has always been the case, why would it have to be kept from other childrens parents? If schools, trans identifying children and their parents knows children with the PC of GR can go into the wrong changing room and toilet, why the secrecy and why is it a shock to other parents?
From a parents point of view, it looks as if schools have commissioned outside agencied to teach children about GI, told them that its their right to use opposite sex facilities in school, and then allowed an increasing number of children to do so. All the time keeping the teaching material and the practice away from parents.
If is was a basic assumption, why doesnt everyone know that?
It looks like schools were making an assumption, and then later saying that there was no guidance from government. But would there be if the assumption wasnt based on the law, and government and parents didnt know the extent of what was going on?
What would be good to know if schools allowed children to identity into the wrong changing rooms and force preferred pronoun before or after seeking advice from the government.