A truism about middle school, high school, and college orchestra conductors: During rehearsals, if the conductor isn't acknowledging obvious intonation or rhythmic miscues or murmurs only, "Just keep going," or "Let's go on," a tongue-lashing is almost certain to follow at the end of the movement. This doesn't usually happen when an orchestra sight-reads a piece that was just distributed, but after that...
An example: One of my high school ensemble conductors spent week after week rehearsing the first and last movements of a symphony, resulting in excellent concert performances. As for the second and third movements, however...
...The conductor waited until two weeks before the concert to start rehearsing them. The results were less than excellent. During a rehearsal of the second movement, he conducted while maintaining a grim expression and saying very little, until the end.
"That was dreadful," he told the orchestra. "I thought we could just play through it..."
At that moment, I suspect he realized that conducting an ensemble of kids necessitated different pacing than conducting a professional ensemble of adults.
