Boy, did you hit a nerve. Unfortunately, most involved with kids sports think that 3rd, 4th, 5th, 6th, and 7th grade kids should play on the same size goal and with the same size ball as the NBA. Makes sense doesn't it? That way kids twist and contort their bodies and develop a horrendous shooting form trying to muscle a ball into the basket in a game whose final score resembles a soccer match. Meanwhile, players who develop ball handling, passing, defensive, and other such trivial skills will forgo the limelight to the big kid who has no such trivial skills, but does have the strength to regularly muscle the ball up to the basket. OK. I'm done. Sorry. I would recommend 7' to 8' using a 27.5 inch ball progressing up through 7th grade which, in my opinion, is a transition year where they can play with the regulation (29.5 inch) ball or the 28.5 inch ball and use a basket 9' to 10' If it's in your backyard. Increase the height of the basket based on the strength of your child. He should be able to get the ball up to the basket consistently while using proper shooting form. More importantly, drilling the aforementioned "trivial" skills should get more time than shooting drills.