PA28 NOSE GEAR COLLAPSED DURING LNDG.

Narrative

WE (MYSELF AND COMMERCIAL STUDENT) DEPARTED ON A VFR FLT. THE PURPOSE OF THE FLT WAS TO REVIEW THE MANEUVERS REQUIRED FOR HIM TO PASS THE COMMERCIAL PRACTICAL TEST. 1 HR LATER WE ARRIVED AT ZZZ FOR LNDGS ON RWY 23; TO PRACTICE 'PWR OFF 180' LNDGS. THE WX RPTING AT THE ARPT HAD RPTED WINDS OF 180 DEGS AT 5 KTS. A CALL TO THE UNICOM CONFIRMED THAT RWY 23 WAS IN USE. ON THE THIRD LNDG THE STUDENT ACCOMPLISHED EVERYTHING TO PREPARE THE PLANE FOR LNDG; THE 'GUMP CHK;' INCLUDING MAKING SURE THERE WAS '3 GREEN.' THE LNDG WAS PERFECT IN EVERY WAY UNTIL THE FINAL MOMENT OF THE LNDG. THERE WERE NO HOPS; SKIDS; OR SIDE LOADING OF THE AIRPLANE. WHEN THE NOSE GEAR CONTACTED THE RWY IT COLLAPSED. THE PROP AND BOTTOM ENG COWLING THEN IMPACTED THE RWY AND THE ACFT SLID TO A STOP IN A NOSE DOWN ATTITUDE (THE 2 MAIN GEARS REMAINED IN THE DOWN AND LOCKED POS). UPON EXITING THE ACFT MASTER AND MAGNETOS WERE TURNED OFF. BOTH OF US EXITED THE AIRPLANE UNHARMED. I BELIEVE THAT THE CAUSE OF THE INCIDENT (AS IT WAS CLASSIFIED BY THE NTSB) WAS A FAILURE OF THE NOSE GEAR. THOUGH IT INDICATED DOWN AND LOCKED; THE GEAR SOMEHOW FAILED AND COLLAPSED.