I think both types of schools are great but it is important to find that bit of balance for your child. All play and no structure is just as much of a problem as compared to a school with too much structure. Since your child is feeling happy in his current school, maybe you can share some of your concerns with the principal and hear what she has to say.
If you are thinking of changing school, do take some time to visit the different schools and speak with the centre principal or director and understand how much emphasis is placed on structured learning and free play.
At the end of the day, I think most importantly is that your child has to be happy going to school and learning. Hope this helps. :)