After touchdown from a left wing low landing, the student pilot, who was flying the airplane from the front seat, allowed the airplane to veer left. The instructor pilot, who was in the back seat, took control of the airplane, added full power, and pulled back on the stick in an attempt to avoid a runway light. The airplane cleared the light at a slow airspeed; however, its right wing immediately dipped and struck the terrain. The airplane then spun around and came to a stop. Examination of the airplane revealed no anomalies which could have contributed to the accident.