What I think most important is if the school has resource to accommodate my child’s need, and the peers would be in reasonable level to make group activity worthwhile. Failing those, the academic level of a class can be less meaningful.
In my daughter’s community college English Composition 1A course, the professor is going to give one 10-minutes individual review session per student for the final paper only. The rest papers were peer reviewed by classmates, which were entirely consisted of “I like your argument” and “Good job” with couple of punctuation corrects. I don’t see how any boarding school with average class size of 15 or so can fail at that.