Do they consistently use this type of rehearsal technique or was it just a one-time occurance?
I would make it known to the head director that you were unhappy with the rehersal technique and disappointed that so much time was wasted. I would be sure to back up the comments with examples of how things could have been done better so that they are aware that you are not coming to them with a problem, but with solutions to the problem as well.
Other than that, there isn't too much else that you can do. The head director made the decision to run the show that way. One thing you might want to consider is that the show was run that way as a way to break the monotony or blow off some steam. It is late in the season and I'm sure the kids are tired of doing the same thing over and over. This might have been a way to get them excited about the show again and give them a change of pace by having some stupid fun before they all start hating each other.
In the groups I've taught, I have found that by the end-of-October/beginning-of-Novemeber timeframe the kids are usually sick of each other and have very down attitudes about the program in general. We've always had to break the monotony a little to get them back on track. Sometimes this would involve the kids playing through the show but on different instruments, or by having the instructors march spots in the band. The kids normally get a kick out of it and they seem to get pumped up enough to finish the season strong.
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The Cavaliers - Baritone 1993
Hawthorne Caballeros - Baritone 1988, Contra 1989-1995, Bass 6/5 1996-1998
Pequannock HS - Marching Instructor 1995
Saddle Brook HS - Percussion Instructor 1995
Lodi HS - Percussion Instructor 1996-2003