You're not allowed to give out 100% copies and retain originals, even if you take them up later. You can copy up to 10% of a work for it to fall under fair use. Whether or not you destroy the copies afterwards is immaterial. You're creating illegal copies, full stop.
Does that stop virtually anyone? No. But the law is the law is the law.
Here's the ridiculous part. The KID is allowed to make THEIR OWN copy for rehearsal purposes. Or, if you handed out the method books to each kid but asked them to use the "copy" it's a rehearsal purpose copy, and THAT is legal, provided the student has the original in their possession. But if you retain the originals yourself, it's against copyright.
It's all part of why TECHNICALLY you're required to have original copies of your music at UIL. Even though, again, virtually no one checks.