Yes I have seen this done and if it was my kid he would NEVER play for that coach again EVER Period and neither should you. The worst thing you could do to a kids arm at any level is warm him up, have him pitch, cool him down and have him pitch again.
The warm up is the key once you gear up no matter if you throw 10 or 100 pitches once you get to the point where you pitch your done for the day. Again why would you ever need to win a game that and risk injury to a kids arm. Ask any pitching coach or trainer on LI or in Baseball and they will tell you the same thing that is a no no.