Auto-distributing challenges, investigations, and games

On many sites, such as MathPickle, resources are categorized by grade level. If a resource is labelled appropriate for 2nd graders, we don't know where in the 2nd grade curriculum the resources should be placed, without carefully inspecting it. Thus, if we want to place the resource automatically, we'd place it in the 3rd grade curriculum. Thousands of resources are already placed in this way. Ideally, I will eventually inspect them all, placing them exactly where they belong.