It's not the ref's responsibility to keep the score down, just to enforce the laws of the game. The coach should try pulling players off the field until things even out. You have to have seven on the field including the goalie. I like this approach better, because I don't like telling kids not to try to score. That can hurt you later. If you tell them to play one or two touch, that usually produces more goals. If you are two or threeplayers down, you can still play good soccer, and keep the score respectable.