During takeoff on an instructional flight from a 2,200 foot long by 80 foot wide private grass runway, a loss of control occurred and the airplane struck the ground and nosed over. Neither the student pilot or flight instructor was injured. Postaccident examination of the airplane revealed that it had been substantially damaged. According to the flight instructor, the airplane had 10 degrees of flaps extended for takeoff. After the student rotated the airplane for takeoff, the student pilot used right aileron instead of right rudder. The airplane began to slip to the right, the right wing "dropped"; the airplane then" pitched up", and entered an aerodynamic stall. The airplane then pitched nose down. The flight instructor tried to correct using left aileron, rudder and elevator. The airplane struck the ground with the left wingtip and nose, and then nosed over about 60 yards off the departure end of the grass runway. At the time of the accident the prevailing winds in the area were in the process of shifting from a crosswind to a right quartering tailwind. The instructor advised the NTSB that he "should have taken control sooner".