In my experience, IEP teams have been very happy to accept outside evals in lieu of school-based testing. The schools I've worked in typically add classroom observation, teacher reports, and record review. In my state, the submission of a comprehensive outside eval also starts the clock for a team meeting, just as completion of a school-based eval does, which then must be convened within 10 school days. Your state regs may vary.
There is a whole lot of "teacher data" in the report. Both narrative and results of BRIEF and BASC, maybe some other things--I'm kind of fried and don't remember it all. I don't think any reasonable person could look at what the teachers reported and claim his disability isn't having an effect on his education.
Also, this evaluation was done on recommendation of both program coordinator and program counselor, using a person they recommend. That should help, I think.
