I'd also try to figure out what more the school would do for him if you had IQ test results. It may or may not be worth spending the money in terms of getting actual accommodations from the school. For us, I suspect that dd13 would have gotten all of the accommodations she's had including a grade skip even if we didn't have IQ test results, but I've been a lot more comfortable with the bigger type of interventions such as skipping a grade knowing that her IQ is high as well.
Is there any possibility of subject acceleration at his school where he goes to a higher grade level for some subjects?
Re unraveling kids, my dd13 fell apart on us in 1st grade. For her, b/c she was younger (i.e. -- not a 3rd grader), she cried in class, told us she wished she had never been born, and generally fell apart emotionally. Actually 3rd grade wasn't a great year either and I do recall her holding it together better in class (no crying), but she got a lot of stomach aches that were so bad that she kept going to the nurse's office and there were a few times when I picked her up from school and she started just shaking in the car.
