Flatbushmom: Two things occur to me, though they may not apply to your son:
1) A child wanting to be accepted socially can’t afford to be arrive at school unkempt. Make sure he has his haircut, looks neat and presentable, etc. A minor thing, perhaps, but important.
2) Is he in the correct class for his age? My son was the youngest of his class. We kept him down a year since we felt it was best for him. I noticed that his social standing changed from fair to excellent.