THE STUDENT & INSTRUCTOR (CFI) WERE ON A DUAL INSTRUCTIONAL FLT IN PREPARATION FOR THE STUDENT'S 1ST SOLO FLT. AFTER RETURNING FROM FLT IN THE LOCAL AREA, THEY ENTERED THE TRAFFIC PATTERN TO LAND ON RWY 12. DURING A FINAL APCH TO LAND, THE STUDENT FLEW THE ACFT TO CROSS OVER THE THRESHOLD AT ABOUT 3 FT AGL & LAND ABOUT 200 FT DOWN THE RWY. AS THE ACFT WAS CROSSING THE THRESHOLD, THE RIGHT MAIN GEAR STRUCK THE TOP 1 FT OF A MOUND OF DIRT. THE GEAR FAILED. DURING THE LANDING THE ACFT WENT OFF THE RIGHT SIDE OF THE RWY. THE CFI REPORTED THAT DURING DEPARTURE, THEY MADE AN INTERSECTION TAKEOFF, AND THUS, DID NOT OBSERVE THE MOUND OF DIRT ADJACENT TO THE END OF THE RWY. THE CFI ALSO SAID THE MOUND WAS THE SAME COLOR AS THE SURROUNDING TERRAIN & WAS VIRTUALLY INDISTINGUISHABLE. MOUNDS OF DIRT HAD BEEN PLACED AROUND THE APCH END OF RWY 12 IN PREPARATION OF REPAIRS. THE MOUNDS WERE ABOUT 4 FT TALL.