Ex teacher here.
You have a bigger problem on your hands: Less aware teachers, and other adults too, are going to expect your son to be more mature/emotionally developed than he is at his chronological age. They will expect behaviors he does not yet possess. When he's in kindergarten, other teachers on the playground may assume he is in, say, 2nd grade and respond with those kinds of expectations. If this happens to him a lot, he may feel pressure.
Just be aware of this, talk to his teacher about it, and a little about it with your son.
You have a bigger problem on your hands: Less aware teachers, and other adults too, are going to expect your son to be more mature/emotionally developed than he is at his chronological age. They will expect behaviors he does not yet possess. When he's in kindergarten, other teachers on the playground may assume he is in, say, 2nd grade and respond with those kinds of expectations. If this happens to him a lot, he may feel pressure.
Just be aware of this, talk to his teacher about it, and a little about it with your son.