Greenfields Junior High School is a junior high school located in Paradise Valley, Arizona. It is the older of the two junior high's in town (the newest of the two being Danielle Atron Junior High School).
Greenfields Junior High is mentioned in the show, but never physically seen. Vince Carter and Dave Watt both mention having attended Greenfields in their junior high years. Dave goes as far as to mention that he didn't remember Vince, but that "there was this one kid, Vinny, that everyone was beating up on". It is implied by Vince's facial expression after Dave says this, that Vinny and Vince are the same person.
It is also fair to assume that other adult characters, including the likes of Danielle Atron, Barbara Mack, and George Mack all attended Greenfields as teenagers, as it is the older of the 2 junior high schools.