I was already the youngest in my class (Sept birthday literally the day before school started) and also one of the smallest (family history suggests there must be a late-bloomer gene somewhere on the Y-chromosome). So when my mom was asked for permission to skip me ahead in school, she rejected it.
And I think she did the right thing.
My school experience is best described as "hellish" until 7th grade, when I began junior high and finally got some differentiated curriculum with honors classes. Socially, I constantly had MAJOR problems with bullies until the end of 8th grade, at which point my body started catching up. I also began dating here and there in 8th grade.
It was because of those social concerns that my mom held me back. It's important that everything started getting better as I got older, so I gained the confidence I needed to move on to bigger and better things. I'm sure that if I had been skipped, I'd have had bully problems all the way through school, and I'd never have kissed a girl. I don't know where I would have found the confidence to get on with my life, because in the things I've done since, I've certainly needed it.
So, informed by my own experiences, I'd say if your boy is in 4th already and middle school starts in 6th:
- Hang in there, it'll get better soon.
- In the meantime, see what accommodations you can wring from the school that don't involve a grade skip.