There are so many different things that you can do. It really comes down to how you plan on using the sound system. Does it need to be portable or will it stay setup and stationary? Are you looking for just amps and speakers? Do you need a mixing board as well? Is it used in 1 venue or multiple? Are you the only one using it or will other teachers have access?
Easiest place to go look and see what is out there is musiciansfriend.com They have some great ones, and they have some $$ making junk that doesn’t work. Good place to browse.