How do you compare a PG and a 9th grade re-class. A PG is a grown man. Once kids Physically mature, with lifting and training there can be very little difference between an 18yo and a 20yo. My son is an 18yo freshman, just as strong and fast as juniors on his college team. Just lifted like an animal and closed that gap. The potential Physical differences between a 13yo and a 15yo are enormous, and down right dangerous. A physically immature 13yo can never train his way to physical parity with a 15yo, his body is simply not producing the testosterone needed to make this happen. This is the very reason these scumbags hold the kids back, to exploit that physical difference. Nothing more than another form of bullying. NOW, do you get the difference? Of course you do, that's why you held him back.
