If you have a small child and have tried buying them a desk then you probably know how expensive they can be, especially considering they'll quickly grow out of it. So, consider making your own. All you need are a couple of legs, which you could get from the store or an old table, and a bread box. The bread box is pretty much the same as a secretary, only scaled down.
Throw a fresh coat of paint on everything and attach the legs and you have a child's desk. Now, if your child actually uses it is another matter altogether.