The instructor pilot reported the student had approximately 30 hours of prior flight time in the accident airplane. The instructor and student were practicing tail wheel landings. On the third landing, the student touched down normally. During rollout, the instructor advised the student to lower the tail to eliminate tail rudder effectiveness. At that time, the student applied brakes causing the airplane to skid off the right side of the runway. The airplane overturned and came to rest inverted approximately 4 feet of the runway edge. A post-accident examination revealed the airplane sustained substantial damage to the firewall and vertical stabilizer. In the instructor's written statement to the National Transportation Safety Board he noted that the accident might have been prevented if he taught breaking effectiveness to lift the tail during high speed taxiing instead of during landings.