I wanted to post an update in case this can help anyone else...and because I'm so thrilled that I decided to pursue this!
I contacted the school guidance counselor, and explained that we were surprised DS didn't do better on the OLSAT. After he went through the standard "he didn't do poorly," he eagerly offered to pull him out of class to do an individual test. He called me back 40 minutes later after administering the KBIT-2 and said he did "exceptionally well" and was surprised at some of the things he knew. He scored 137 verbal, 124 non-verbal with a 135 composite. He'll be moving on to the next round of gifted testing, which is an individual achievement test, where he'll have to score 95% or higher and at that point we can give approval for an IQ test by the school psychologist.
I'm so glad I trusted my gut and made that phone call. And I'm super thrilled that the guidance counselor was responsive. I can't wait to hear what my son has to say about it when he gets home from school!
