GMS...do you think you get listened to more because you are a teacher? I do wonder why there is a reluctance to listen and, in want of a better explanation, I can only ascribe it to laziness or unwillingness to help.
Interestingly, I too have a 'passive' child and I think this is a key feature of whether you get appropriate help or not. Anyone disrupting the class or causing the teacher problems, creates needs for the teacher and hence has their needs met.
A child who causes no problems, creates no needs for the teacher, and therefore has no needs. Seems to be a common problem.
I think a way forward would be a more prescriptive and inclusive system - e.g. before a child gets an IEP, there must be a meeting with parents, parents have a right to be involved in IEP target setting (SEN COP sort of says this but it is too wishy washy).
There should also be more openness about budgets - what is delegated, is it ringfenced, what is it being used for, how many hours is a child on SA, or SA to get from that budget etc. Accountability is key. This is public money after all.