I agree a measured approach is the best as I've said before and as giveme indicates.
However, we have to be realistic too about the system we are working.
If your child is an over 'difficulty' in some way for school or teachers (e.g. behaviourally), than parents often feel very grateful for schools for accomodating them. This may (not always just may) make everyone more likely to work together to secure help as it is in everyone's best interests.
'Hidden' disabilities are much more difficult. Help maybe necessary for a child but the consequences of inaction seldom touch the teacher and this is the kind of situation in which parent and teacher may come into conflict.
Further, as a newly appointed governor with a poor personal experiences of the SEN pathway in my son's school, I can see that obligations are not always ignored, but they are seldom truly understood.
How many schools follow SEN COP regarding IEPs?
How many follow SEN COP relating to the pathway and parental inclusion?
How many schools understand the new Equality Act?
How many schools have published Disability Equality Schemes?
These are fundamenal statutory obligations/guidance and if they were implemented, there would be less parent/teacher conflict.
As it is, lack of knowledge, absence of training (wholeschool), lack of resources and, sometimes, inclination, create a poor starting point for a mutually supportive and collaborative approach