Reply To: Using Original Parts
I am not an authority on the topic, but I believe making a rehearsal copy (to give to the students) is OK as long as you use ( or at least have available) an original copy for each student for performances. I believe you just have to collect these copies and destroy them after the performance.
There is some additional information here:
Also, for any music that is still in print you can usually order replacement parts. Check with your music distributor. I had to purchase a replacement mallet part earlier this year, it was $2.50
I think if you do use originals, it is OK to require the students be responsible for paying the replacement fees. Just make sure they know in advance.