Are there any good French Heavy metal bands?
Gorod or Gojira are both French but they are both death metal bands and thus might be considerably less accessible than you wanted. Wormfood might work because they actually sing (well they utilize harsh vocals) in French, however, though I don’t remember the exact lyrical content off hand they are probably largely school innappropriate due to certain themes that appear in their music (ex: Bum Fight, Vieux Pédophile, etc.) additionally they are a Progressive Dark/Death Metal. Actually, Agressor would probably be a good fit, they’re death/thrash and they utilize harsh vocals but they might be a little more palatable for your class instrumentally if nothing else.
