Children are the most creative in this world, for the simple reason that they are not influenced by anyone. Their creativity comes from the modest joys of life - color, sand, clay, puppies and other things that most of us have stopped noticing.
Ask a child about his artwork once he is done. More often than not, it will be an exaggerated story expressed with animated hand-actions. They like everything to be larger than life and there is a reason to that too. When you look at the world from their eye-level, everything seems l a r g e…the people around, the cars, the furniture, the trees, etc. They believe that most things are larger than them and thus, like to portray a lot of 'big' things in their stories. Notice the words million, zillion, big, thousands, huge when they are telling you about something.
However this also makes them feel more connected to small scale details which we would tend to miss out on... crawling under the table, playing with low-height switches, patterns on the floor, insects to name a few.
Thus, it becomes important for designers to work in the "child-scale". A simple experiment to experience this would be to get on your knees and walk around the room…the ceiling will feel higher, the window inaccessible, the wash-basin too high to reach, the door handle unreachable and the dining table chair too low for comfort.
An essential thing to note when designing for children is their growth. If the same child is going to use the space for a long timeframe (5+ years), like a bedroom, then the space needs to be able to accommodate the child's needs through the years. However, in the case of a school, where a constant age-group of children is utilizing the space, the overall design can be more permanent.
Two most important people to connect with, while designing a space for children are the children themselves and the adult concerned (parent or teacher). If you are neither of the two, the best thing would be is to spend time with both. You will learn more than what any book can tell you. Participation of users in design just helps us learn and design better!