I am inspired by the Baupiloten group in Berlin which have designed the kindergarten Taka-Tuka-Land.
The architecture group has been involved in numerous education designs which is worth looking at:
http://www.baupiloten.com/ger/projekte/taka/Main_taka.htm
The angles at the entrance create little cornors of curiosity. The lack of curves reminds me of my childhood playgrounds with timber, chains and bark- no need to be too precious with the kids!