I like the idea of the wood like fence. You could have one pannel for every child in your classroom and then use it as a growth chart for toddlers. When the child moves up or leaves the centre you can give it to the parents. Use Pallet wood.
Loaf's timber Greta bed is designed for kids. It's made from solid reclaimed fir recovered from old buildings for a nice rustic look and is hand-finished so that no two are the same. Frankly, the most stylish kids' bed around