My DS has asked to change form class (Y7) because of continuous disruption by a small group, which does not appear to be improving despite those individuals being 'on report' etc. DS was in top sets for everything in Y6, but this year streaming has been stopped in non-core subjects. No idea why. Head of Year doesn't seem to know either 
He is coming home frustrated, sometimes in tears, saying he is no longer enjoying any non-streamed lessons.
We have a meeting with Head of Year soon, to discuss this, & she is already aware as we raised it last term. She described it last term as 'low level disruption'.
Not been in this sort of situation before, so wanted a MN opinion on whether a change of form class is a reasonable request for us to make, given that things are getting worse, not better, in his classes.