I've liked the Aaron Cole chorales for a decent number of levels. Could be excellent for a high school group in that setting. It begins with easy enough chorales my second JH band can handle them with some work. The more difficult ones I used to use with my JH top band. Best part is they're FREE! (Google them)
If it is JH I would tell you to look at the new Making Music Matter Book 1 that was released last year. There is no way that those can be considered an effective beginning band method, but they're actually excellent for a NV JH band that missed some concepts first go around. My JH NV group grew more last year than I can ever remember them doing and I believe it was in a large part due to that!