OK, it might help him advance from the completely helpless infant that some are when they first start, all the way upto baby seal level. But at the end of the day, when its all said and done.... hes still just a baby seal when he gets to the MA.
Theres only so much that boxing with another 13yo whos just as clueless as you are will do. And without your coach standing next to the ring (which this newb arena would be doing: taking the coach away), showing you what you're doing wrong, you won't ever get to the point where you can compete in a tournament and win.