The certified flight instructor (CFI) and private pilot student were conducting tailwheel certification training. During the third flight of the day, after practicing 3-point landings, the student pilot was performing an additional 3-point landing after having just practiced main wheel landings. The CFI described the pattern and approach as being normal. During roll out and while slowing the airplane began to drift left. The CFI called for right rudder and the airplane began drifting right of centerline. After calling for left rudder the CFI attempted to regain control using rudder and power. The airplane entered a violent turn to the left, exited the runway, and flipped over going down an embankment. The right wing spar and horizontal stabilizer were bent.