Well. Our HT once 'banned' (it's a question of perception) all parents in the class from talking to the class teacher about reading.
This was in Y1, with a NQT. Same as in Reception, where this had been encouraged, parents had been commenting in the reading record when they felt their child had been reading the books on their level very easily. Sometimes directly, sometimes indirectly suggesting that the teacher listen to the child read (which happened only rarely) in order to see if they might be put up a level. As in reception, the parent volunteers who changed the books would flag to the teacher whenever there was such a comment. Just making the teacher aware, and saving the teacher from having to read all comments in all reading records, when most of them just said something such as 'read p 1-8'.
But it appears the teacher felt stressed by these occasional, polite requests. (Just to reiterate, nobody asked for their child to be moved up a level, just for the teacher to listen to the child read and make their own assessment.)
Parents were invited to a meeting, on very short notice (next day), with the HT and literacy person. Class teacher was not there, as she was feeling too stressed. At this meeting the HT stated that it was of utmost importance that the children read every book of every band, so there was never any question of perhaps moving up a level, and therefore - and because Y1 was about phonics rather than about reading - the teacher was not going to do 1-1 reading with any children except those who were most struggling. Seeing as we now all understood how it works, could we please refrain from talking to the teacher about our children's reading (and refrain from writing any comments in the reading record too - they would not be read by anyone except the book changing volunteers).
From that point onwards the teacher didn't do 1-1 reading with any children except the 'daily readers' (who she heard maybe once/week).
And from that point onwards nobody moved up the book bands except when they had read all 50 or so books on their level.
So yes, there was a reason for the HT banning us all from speaking to the teacher (about reading). I just don't think it was a very good reason. And if I hadn't been able to make that short notice meeting that was called, I might well have experienced it as the HT banning me personally, rather than everyone.
Some teachers are poor. Some headteachers aren't great either.