Thank you, DeeDee! I appreciate the advice. He usually does very well at self-management. Every so often, he gets into trouble through being bored. That has only happened a few times, though, and I've been sending books and activities for him (his teacher is also letting him do reports).
He tests in the normal range in speech and language assessments now, but that was the area in which he had the most severe delays (he used to have profound delays, using the technical description). I've wondered if he might still be having a little difficulty with more complex language like on an IQ test (perhaps with instructions or with questions that require a verbal answer). His teacher says his vocabulary is impressive, but the speech and language assessments seem to test very simple concepts and I definitely wonder if he might be having a harder time with the complex verbal instructions.