Taiko, as we know of it today is often performed and practiced with a bunch of others.
This is not so unique, as you find orchestras and symphonies with a group of musicians that use the same instruments.
BUT, classical musicians have instruments that can be practiced at home...taiko is not well suited for that.
SO, for most students, class is the only place where they get to hit a taiko.
Within practice, allow each student to hear for themselves what their playing sounds like.
If you are doing a drill, take a a few minutes to allow each student to play the same drill solo.
This alone will bring to light many things that even teachers couldn't have noticed when students were able to "hide" themselves within the sound of the whole.
Also, by creating a situation similar to "performer - audience" by isolating one student, this sort of practice helps prepare a student to play for others on stage.
Additional Steps:
- Adjustments - fix or change one thing that will noticeably change their sound or playing, and have them do the drill again.
- Teacher Plays on Same Drum - take turns with the student to play the same drill on the same drum (best if you can play left-handed on naname). This eliminates the possible excuse of "my drum sounds different than others."
Kumidaiko is a Group Effort.
But the group's sound quality is determined by the quality of the individuals that contributes to the whole.