The pitch of a flute changes considerably depending on the angle at which students blow into it. I often see flutes with a high pitch and the joint part pulled out by more than 2 cm, but try changing the way students blow into it to find the angle that produces the best tone. The pitch should also match.
  Also, check that the cork inside the headjoint is not misaligned. The cork of an instrument that has not been maintained for years may have deteriorated and become loose, and may move easily. When a student cleans the instrument, they may unknowingly turn the screw (head screw) at the end of the head joint, causing the cork to shift position.
  Check it about once a year.

  For clarinets and saxophones, if students start practicing using a reed that is too thin, it will sound when students blow lightly, so their breath and embouchure will never become strong and they may not be able to raise the pitch to the standard.