I agree with what the others have said about the teacher making the difference. I would also say that the relative LOGs of the other kids makes a difference. If there is a huge range, it is more work for the teacher. My DS7 transferred midyear from a local nonGT school with 22 kids to a school for HG kids, where he makes the 29th. My DS is thriving at the new school, but probably most of it has to do with a teacher who was willing to take on another kid, who really gets HG kids, and who groups kids by ability. In our school within a school, a planned extra class in I think 4th didn't happen, so that classroom has 34 kids! I visited the classroom, and that teacher also seemed amazing. So for us, there has been no downside to the big class size, since everything else has been so positive (learning with intellectual peers, getting in reading groups at his level with peers, learning appropriate math, etc., etc.).
I recommend asking lots of questions on the tour. Ask the students too, "What's it like being in such a big class? Is there anything you miss?"
