My feeling is always to go with what works for the moment. This a PG or near PG child, 6 good months is a victory, let along a whole year. If you leave him in a bad situation, he may conclude that school isn't for learning. When he is older, he may no longer want to 'learn in school' anyways. There are lots of interesting things to do in school besides learn academics - some of these things build character, and some destroy it.
Just go into it knowing that a school that make the cut off at 127 is going to have the majority of it's students between 127 and 134, which is still a long long way away from what would seem normal to your son, but still a lot closer than where he is now. There may be a teacher there is open minded and that will make all the difference. It seems so simple to find out here the child is, and then met their needs, but in reality, it is difficult, and takes trial and error.
Best Wishes,
Grinity
