We're facing something similar with my 19 month old. He's not very verbal, but it's clear that he interacts a lot more with older kids and he won't even look at or consider kids his age.
This is totally normal. All kids that age appear to be more advanced socially when dealing with an adult or older kid than when dealing with a peer. This is because the older person "scaffolds" the interaction.
So, a couple of points from this. First, just because a kid will socially engage with older kids but not agemates doesn't mean they're socially advanced. (Although of course some kids *are* socially advanced.)
Second point: Mixed age groups are good! For everyone! It's a much more natural way to grow and be socialized. Same-age groups are a very recent, artificial invention.
But, then, third point: In a classroom full of 2 year olds, a LOT depends on the teachers. Good preschool teachers will spend the entire day with endless patience coaching the kids to successfully interact with each other, providing the scaffolding they need. "I see that Jayden has one idea, and Phoebe has a different idea. Phoebe, what could you say to Jayden?" One nice thing about this is that it works even with two kids at different levels of social skills.
Also, a good classroom will have plenty to engage an eager mind -- art, caterpillars, dinosaurs, gooey stuff, plants being grown, books at a variety of levels, songs, dancing, drums to bang on . . . A lot of the problems being described in this thread sound like problems with the classroom, not with the age of the other kids.
