Not exactly that similar but DD3.10 has been going to a nature-based program for a few months and she'd been spending at least half of her time with 6/7 year olds although her BFF is her age-mate. One thing I notice is that socially, she's been learning awfully a lot from the older kids and that can come with its own challenges. I don't know if this is related but she's been expressing lately that she doesn't want to grow up and wants to stay 3 forever.
If I could make it happen, I would prefer to see DD with children closer to her own age who share her (intense) love of learning but right now, that doesn't seem to be an option.