This seems plausible. DD stayed at a play based pre-school until she was almost 6. She spent her days playing dress up and drawing and was as happy as could be. If she wanted to learn about dinosaurs or animals or whatever she could do that. On the whole, I would say school has made her rather miserable. If you have a naturally curious mind it is plausible that the earlier you are put in the educational system the more miserable you become.