IME, Teachers are defensive and secretive. Trying to get through to them or information from them is like banging your head against a brick wall.
But why is this?
Well, successive governments like to bark on about 'doing something about education' and focus on changing things noticably so they can look like something is being 'done'.
Then all society's ills are blamed on teachers. Young people are bad bad bad, and it is all the fault of their education.
So, rather than look at their own policies and effects on society, governments begin inspections and observations of schools and staff and 'training' on the latest strange idea that is based on the whim of the education secretary rather than any evidence.
Teachers are contantly being held account for whatever it is the latest government wants them to do, for reasons that they aren't completely sure of, and they never get to grips with the paperwork for it, because it changes every year.
So when parents ask questions, hold them to account etc. they fob them off as quite possibly the teachers either don't know the answers yet, or don't want to have to explain a system they aren't comfortable with or haven't even yet GOT a system.
And they are frightened of criticism. Because they are blamed enough.
What they seem to want, is for everyone to get off their back and allow them some space to try and make a difference to the children they work with.
And that is probably why they hold on to their 'assumptions' that their internal belief system and 'professional opinion' is the true value of what they deliver.