I wouldn't say that most black American English teachers speak ebonics all the time.

In fact, I tend to feel more irritated by the 'wigger' types teaching ESL; they might not talk like that whilst teaching the kids their ABCs, but often will when they're trying to act like some kind of gangster in one of the local WeChat groups. I often just hope that they end up getting deported thanks to them being excessively blasé about smoking/selling weed or doing other drugs and stuff.