How many times have you heard this: "We went to UIL, and the warm-up room was freezing, and that's where we tuned. Then we got on the stage and it was boiling hot, and it screwed up our tuning." Well, that tells me that they do too much "work with the tuner", and not enough listening and matching pitch. There isn't going to be a tuner on stage, but if the kids listen to each other and match pitch, then it won't matter which room was warmer/colder than the other. Judges used to tattoo all over my sheets, "intonation, pitch, tuning", right before they put the words "Three" or "Four" for my ratings. Once I laid off the tuner, using it only sparingly, and had the kids focus on listening to each other and matching pitch...those judge's comments went away, and the words "One" or "Two" ended up in the rating space. It isn't easy, and it needs to start at the MS level for it to become second nature at the HS level.