Considering how cowardly the average administrator or bureaucrat is, and considering that the parents went all the way to the school board, if there was any question or leeway here, the grade would have been changed. The fact that it wasn't by the powers-that-be is a relatively good indication that there is more to this story than was printed. But, of course, let's believe Yahoo news blindly!
Yahoo has more credibility then the average public school teacher