Both airplanes were in the tower controlled traffic pattern; one airplane was on a left downwind with a CFI, dual student, and a student pilot/observer occupying the rear seat; the other airplane was on a right downwind and was being flown by a solo student pilot. The local controller cleared the solo student pilot on the right downwind to land following an airplane to the student pilot's left. The local controller then cleared the dual student's flight to follow the solo student airplane's on the right downwind. The dual student's flight acknowledged the clearance, but both pilots misidentified the solo student's airplane and began following the airplane ahead of and to the left of the solo student's airplane. After the local controller cleared the solo student to land he then cleared the dual student's flight to follow the solo student's airplane. The dual student's flight followed the airplane ahead of the solo student and began to turn onto the final approach. Shortly thereafter the solo student's airplane descended onto the dual student's airplane. The solo student landed on the runway without further incident. The CFI in the dual student's airplane executed a forced landing in the open desert terrain, but nosed over during the landing roll.