Here is what USL representative had to say about grade based Lacrosse trend last month in another forum discussing grade based vs age based teams .

""""" The problem with grade-based segmentation in youth sports is, of course, that it's not in the best interests of kids. The different rates of physical and cognitive development at each age varies widely so, in contact sport like boys' lacrosse, it's simply not safe to allow kids of such varying ages and development levels to compete against each other. Nor does it reinforce the fundamental principles of fair play and fun that are essential to player retention in youth sports. Allowing the club "system" and associated recruiting events to determine what's best for your child is not only a clear conflict of interest...it's a tremendous abdication of responsibility by the primary consumers of a child's lacrosse experience - parents """""""""""""

Most people agree with him except the chosen ones and their supporters who like to have children play against younger children to get an advantage they couldn't have going against same age children..But of course only they are allowed it as they had the forethought to hold their children back.