I don't know about edgy midgrade, but I'm not trying to be edge, just write how teens actually talk. Well, okay, I can't write how they ACTUALLY talk in a midgrade book, but I would think stuff like what the Sailor Guardians say would be okay, but, then again, that comes from a different culture, so maybe not?
And I'm calling it MG only based on the expected length, which is about that of books that I've read (the Americanized Sailor Moon novels from 2000, the W.I.T.C.H. novelizations of the comic books, the Riverdale High and Betty and Veronica novels from Archie, etc.): roughly 30,000 words / 120 pages. YA tends to be longer, right?