My son was tested privately first and 2 years later by the school. The results happened to be almost identical. At school they pulled him from class and only did a section or two at a time.So he was very well rested and he missed a lot of class which was an advantage given his situation.
:ur local private tester hired a grad student to administer the test and misdirected us when it came to figuring out what the problem was.
If you aren't worried about unraveling any mysteries I think it is fine to do the school testing. If you do need help then the trick is to fiind a tester who really gets high LOG kids. I have learned over the years that it is hard to know who these testers are. One of those 'I don't know what I don't know' situations.
One advantage of private is that if you child hits any future road bumps you have someone to call who knew your child in summier times.
One advantage of school testing is that it might turn the school psyc into an ally who will advocate for better fit education for your child.
Either way is good.
Grinity