Welcome - and sorry that it is difficulties that brought you here,
A few questions: why is he being sent to the principal's office? Is he yelling, throwing things, being aggressive with his classmates? Is he doing his own thing while the rest of the class is paying attention? Is he saying or doing things that he sees as appropriate responses but which the teacher sees as a challenge to authority or disrespectful? Knowing exactly what he is doing may help us throw out ideas that you might try.
Testing - we had to test privately because the deficits we were seeing in the classroom were not far enough delayed to qualify for testing in the school. If you do go outside the system, make sure you use a professional whose report will be accepted by your school - they don't always accept all outside testing results. Also, if it is to test for developmental issues, your insurance might cover it, they want cover it for academic reasons, but whether for academic or developmental purposes, the testing overlaps quite a bit and gets the results you need.
