During the dual primary cross country flight, the student was making the approach and landing at Prescott. The CFI said that the approach and touchdown were normal, however, the aircraft began drifting to the right in a gradual turn as the aircraft slowed. The student's control inputs to correct the right turn were unsuccessful and the aircraft ground looped in the soft soil off the right side of the runway. The CFI stated that he 'probably waited too long to take the aircraft' from the student, whom he described as 'an excellent student.' Subsequent examination of the aircraft by a repair station revealed that the tail wheel steering pawl was broken and would only steer the aircraft to the right and would not engage to the left at all. Examination of the CFI's logbook revealed that he only had about 150 hours as a CFI. All of the student's flight time was accrued in Cessna 120 & 180 model aircraft.