Thank you all for your responses!

All of the kids in public pre-k are either 4 or 5 years old. Matthew is very small for his age and is turning 4 in a couple of weeks. He is very mature for his age but at the same time is very shy and clingy in new settings.

I'll keep him where he's at and I think it might be time to put him in extracurricular activites. The kid begs me not to take him anywhere but he needs it!