Use rehearsal as more time on faces for everyone. On the times you need to break it apart give everyone else a job.
"Floboes and Clarinets are playing measure 12-20, everyone else note name and finger, percussion air-drum"
"Low Brass and Low Reeds let me hear your part at 30, everyone else fog/air-band"
For those kids who still don't know how to rehearse....sometimes you have to slaughter a lamb in front of everyone to let them know what the expectation is. If they still don't get it after than than FIRM private discussions with those kids outside the room and go up the chain with admin.