Those that are held back for reasons other than sports are usually held back a much younger ages than 8th grade. Like all elitists', it's OK to be against something for others while feeling entitled to do what you want - when you are the greatest, why should the rules for those below you apply?
That rings true to many in this area as the main drivers of playing down in youth sports is the " Character Driven " students/parents of the MIAA private schools in Baltimore.
Classic example of the hypocrisy is the debacle of Gilman football a few years ago. Old Poogy recruited top football players who overwhelmed and destroyed the other MIAA schools, Their solution, not play Gilman in Football. While they are on the winning end with recruitment, alls ok,,,soon as they start getting beaten by bigger and stronger players, quit... And that is at the High School level not youth.