Most high school play calls for a 10 or 12 run rule, after 4 1/2 or 5 innings. I take it your area does not?
I worked a U14 tournament a couple weeks ago in the round robin portion of the tournament, in a game that meant nothing for either team, the visiting team down in the 3rd, in a slight drizzle and it being a pretty windy day, were behind about 20 something to 0. The coach came forward and said "we ain't playing no more". Gutsy call but probably the right one.
I was the UIC and or president of a local BR League for 4 years, our local Umpire Association hounded me for the entire time to establish a ten run rule, I refused, we already had a time limit on all games. The theory here was to allow the maximum amount of time on the field in order to allow the players to get their hacks. I met with coaches regularly and as long as I saw constructive coaching and learning going on I would not bend. In short if your players are competing, learning and most importantly trying to improve, they deserve the most time on the field they can get.