I see this more often in junior high schools than in elementary schools, but there are still schools that continue to have strange customs that I don't understand.
  First, there are bands that spend a long time doing sit-ups and push-ups to build up their physical strength. At a junior high school, there was a school that spent more than 30 minutes of their two-hour practice time on "building up physical strength." It's true that it builds up physical strength, but I think the muscles needed to play an instrument are developed in the process of practicing the instrument.
  I still see people making beeps (or squeals?) with just the mouthpiece of a clarinet or saxophone for several minutes every time before practice, and making freshmen play only the mouthpiece without having an instrument for several weeks (more than a month?), but that doesn't make any sense.
  If you don't have enough instruments and you're just trying to make up for it, then there's nothing you can do, but if you have an instrument, playing it and making sounds is the best musical practice method. And sometimes playing an instrument is even more fun.
  Students can't control their breath or embouchure unless they hear the sound coming out of the instrument. Check for problems with all blowing by the tone. Practicing without hearing the tone is not musical.
  I think it's necessary to explain how to blow with just the mouthpiece to students who are playing the instrument for the first time and help them understand how sound is produced, but once that process is over, there should be no more effective practice method than making sounds with the instrument.
  The same goes for brass buzzing, and I think that doing this only at a loud volume for a long time (especially for beginners) is more detrimental than it is harmful. There is a risk that student's lips will open up and the sound will sound like buzzing even if the student attach the instrument.
  When a student has become quite good at playing, you may be asked to do a special practice for a certain purpose, but in such cases, it is best to explain in detail why the practice is being done and specify in detail the volume and time of the practice.

  Another, although not a practice habit, is a strange sight that I often see.
  A playing style in which the left hand is used to hold down the head of the bass drum before hitting it to completely stop the sound (so that no sound is produced). Depending on the piece, such a sound may be necessary, but the body of a drum or tom is originally made with consideration for the balance of material, depth, and diameter for the resonance and tone when it is struck. If all of that reverberation was lost, the instrument would have no value. The bass drum is also an instrument.
  First, play the sound and let it resonate, and then mute it if the reverberation is too long. It is strange that something that is quite common with timpani cannot be done with the large drum for some reason.