Exactly what EPOH said - especially the first. Their agenda and mandates are driven by their employer, not you or your child. Thus, they can never be an impartial advocate on your child's behalf.

Our psychiatrist is currently working with us to provide documentation regarding clinical reasons for depressed scores on standardized tests - something he suggested as a means to get my son his differentiated work for his Giftedness and not just his disabilities. I promise you, in all the years I've worked with school staff, none of them would go out on a limb to fight the status quo to get the appropriate accommodations because of the reprimands and consequences they feared from their employers,

Having someone outside the system who isn't motivated to put your child in a definable box that works in their system is to your benefit.