Have you spoken with your school's gifted teacher? If not, I would start with her, and get her advice on how to explain the difference between your gifted child and those 8th graders in the study presented by your principal. As for Hoagies, I would recommend searching through it yourself to handpick the most relevant articles related to your child's mathematical talents, rather than just sending a link to Hoagies in general. You could offer books, but teachers and principals are busy, so if you do, I would recommend marking a particular section you want them to read.
And maybe or maybe not helpful, but Tamara Fisher has some good articles on how to respond when you hear some common myths about gifted kids, here:
http://blogs.edweek.org/teachers/un...rning_difference_3.html?qs=tamara+fisherhttp://blogs.edweek.org/teachers/un...kid_not_next_years.html?qs=tamara+fisherA new blog i found:
http://www.byrdseed.com/differentiating-math-lessons-for-gifted-students
