You are right, a six-pointed star is a much more common shape for a hari shiruken than a five-pointed star, but I’ve seen examples with any number of blades between three and seven. I’m charmed by the idea of a TruTV show devoted to “World’s Dumbest School Administrators”.
If “could be mistaken for” were the criterion in the regulation, the little boy wouldn’t be being hassled. The regulation reads “looks like a weapon”, so miniaturization, being made of flesh and blood rather than steel, and the like don’t make enough of a distinction as they would in your proposed “could be mistaken for” criterion. (The folks who wrote the regulation also get a feature in your proposed show, as well as the ones applying it.)