User blog comment:TheSonofNeptune/Is Percy Jackson going to have to repeat a grade in Highschool?/@comment-6064271-20130123230800/@comment-3146930-20130123234613

But Percy is turning 17 in August. In most American school districts, he would mean he is going into his senior year of High School in September (or whenever they start, normally after Labor Day). That would mean that Percy was in 11th Grade when he was kidnapped by Hera.