It's science fair time at my son's school. He's in the first grade, so admittedly there's not a lot that he can do without a reasonable amount of *cough* parental*cough* help. But why do we not have a 'mathematics' fair or a 'programming fair ?
The science fair project format is very confining. You have to propose a hypothesis, tabulate a bunch of results, do some analysis, and discuss conclusions, with nice charts/graphs and other such science cultism. Even if you're interested in something more 'mathematical', there's no real way of shoehorning it into the format. A year or so ago, a colleague of mine was asking me about origami-related projects (because his daughter loves paper folding) but apart from experimenting with knapsack-style algorithms to determine how to fold a ruler into a specified length, we couldn't figure out something that fit into the 'hypothesis-experiment' setting.
Granted, it's a science fair. But at this age level, I assume the whole point of participation in science fairs is about learning something about science, rather than conducting rigorous analysis. You could equally well learn about something mathematical and demonstrate that knowledge. But there's no forum to do that in.