Once the kids are in high school, I age that the grade level works fine. You have kids fighting for jv and varsity spots in high school and the only time something is a little off is a kid there past his true senior year. However, for kids truely 8th grade or younger, the parents need to focus on creating a fair competitive environment by playing based on age. If a kid wants to play up - fine, let him challenge himself, but playing down though any loopholes or hold backs or other method is wrong and against the spirit of fair play. If your kid wants to dominate his age group, tell him to practice and hit the wall, don't have him play down.