Hi Hilary and welcome here,
Where you have really begun the process of becoming an expert on CAPD and education Laws?
Where you will need to take control.
Firstly in regard to testing at the age of 6?
The neural auditory pathways are still in a process of developing, up until around the age of 8.
So what they are unable to do until this age, is to give a formal diagnosis. As it can be simply a developmental delay?
Which the education system use as a legal delay, to providing support.
Yet many audiologists will test before the age of 8.
Where they can identify which particular areas of CAPD a child is having difficulty with.
Where it is made up of various Sub-Types.
Which is what you really need to identify.
Though the fact that mention seating in relation to minimizing noise difficulties.
Suggests that it could be the sub-type of Hyperacussis and Figure/Ground difficulties?
Yet it could also be a Dichotic problem, where one ear is deficient in processing auditory information?
My point is that you first need to get a clear idea of what sub-type you are dealing with?
Otherwise, you will spend many years on a trial and error discovery process?
That your son will have to endure!
So as I said at the beginning, you will really need to become an Expert, so that you explain and teach teachers what to do, each new year.