I would say any age above ten if it's a man press. These zone trapping presses on young kids isn't teaching the defense much. Man to man isn't being taught a lot in younger ages. At least not here in SoCal :)

@Nate Dougherty so true! We see this a lot at the high school level still, and it's really bad at the AAU level because point spread matters in a lot of these tournaments. Coaches should be able to find a positive in all these cases. I tell my high school team all the time, we win or we learn! Losing only happens when bad attitudes take over.