I know it is not spring… but I thought this would be a perfect backpack for gym. And well… lots of kids can use that. Personally, I hated gym when I was a kid. Maybe such a cheerful bag helps to ease the suffering a bit 😉 if you dislike gym as well.
You can find the free crochet pattern of the Spring Petals Backpack on the Ravelry page of Susan Gater.