A PA28 instructor pilot reported that his pre-solo student attempted to turn off the runway at too high a speed and exited the runway before relinquishing control to the instructor.

Narrative

During the landing rollout after returning from a flight lesson the student attempted to turn left on a taxiway at a speed that was impossible to negotiate the turn. Student froze on the controls and made it nearly impossible for instructor input despite my efforts to transfer controls and verbally steer the student back on the runway. Consequently; the aircraft departed the runway/taxiway intersection onto the grass off the left side of the runway. At this time the student relinquished control to me and I was able to safely return the aircraft to the taxiway surface. Tower asked if we needed assistance and I briefly described what happened and said that we needed none. I was not told to contact anyone about the incident. This student is a pre-solo student who is currently working with another instructor who is out of town. This was my first flight with this student. I had been briefed by her instructor as to her progression before the flight and we had just returned from an hour and a half landing lesson at another airport. Contributing factors to this situation are both mechanical and pilot. The aircraft we were in had operable brakes on only the pilot's side and none on the instructor's side. Also; the emergency brake was inoperative. In the debrief the student told me that they had never been told that you are not required to get off on the first taxiway and that you are only supposed to turn when speed permits. This was also a fault on my part as the instructor who should have briefed the landing phase a little more thoroughly. Student inexperience; instructor inexperience with that particular student's habits; aircraft discrepancies; and the student freezing on the controls and refusing to relinquish them were all causes to this incident.