So I'm flying with a new student -- hour 6 -- and we're doing the normal pattern entry. on a 45, closer to the upwind end of the runway, but fairly close, etc. Winds are light but favoring 28, all traffic that has landed in past 45 minutes has landed on 28. He announced 3 miles from the field, entering the pattern, downwind for 28. I can hear other chatter on the radio but no airport ID -- just typical "Yeah, Jerry, I'm over here.." stupidity. We're nearly abeam the numbers when I see a glint of silver ahead -- airplane, our altitude, right at us. "My airplane." I do a right turn out of the pattern (C150, so a right turn lets me keep an eye on him), and watch as hero does a steep 360 then heads for the upwind side. I also hear , "Yeah, uhh, gonna head over to upwind side.." Again, no identifier, no nuthin. I get us back on downwind and see it's a silver RV. Now -- someone please tell me -- why, oh why is it always these blasted RV drivers who feel compelled to do overhead breaks over public use, busy GA fields? I've yet to hear or see a Cessna or Piper or even Cirrus call "Overhead break" and ignore all pattern protocol (though I have had close calls with the same when they mis-called position, etc). Also, the non-standard radio use, the complete disdain for other traffic seems unique among these wannabes. What am I missing?