Thanks everyone for the thoughtful responses. To answer the questions raised...

He's is in private school. He does not have an IEP or 504.

On the opt out, We might decide to see if he can get into the gifted program next year and I'm not sure that he'll do well on the test.

We are happy with his current school but afraid they might discontinue the upper elementary program next year. His teachers said their students usually do fine on the tests but that they don't really show what they know because the format is unfamiliar.

He leans towards the anxious side and I didn't want his first real testing experience to be something he's not at all prepared for. It just seems kind of unfair.