Here is a good Independence Day research question to give your middle schooler: Why does the flag of the United States have five-pointed stars? If s/he figures it out, please ask her/him to put it into the comments, because I couldn't find a definite answer.
The most prominent idea you will find is that Betsy Ross talked George Washington, who sketched six-pointed stars in his preliminary sketch that has been preserved, into using five-pointed stars because they were easier to cut and sew. Which is a great story, except that many more respectable sources say that it isn't true--or, at least, we have no physical evidence to suggest that it is true, let alone to prove that it is true. So, for example, see the interesting article in the Washington Post on "Five Myths About the American Flag," which talks about this matter and other things that people generally believe about the US flag, which turn out, inconveniently, to be false or at least not to be supported by evidence.
However, most sources that I've read seem to agree that it was the six-pointed star that was commonly used at that time. So at least some suggest that the Americans used a five-pointed star simply to distinguish themselves from the European history of six-point stars for flags and crests and such. But, again, as far as I can tell, that is merely conjecture that is not based on any evidence. And according to "Five Myths About the American Flag," the prevailing theory about the fact that our flag is red, white, and blue is that it was based on Continental Army flags, which were based on the English flag--which kind of argues against the "five points to be different"argument. But maybe they wanted some symbols taken from our history and some marks of differentiation?
Isn't it interesting that we don't really know the derivation of one of the most important symbols of our country?