An instructor pilot monitoring his student pilot's second solo flight witnessed the loss of control and departure from the runway which occurred when too aggressive action was taken to clear the runway promptly.

Narrative

I was conducting a supervised solo when the student; upon landing; skidded off the runway. Conditions were optimal with winds calm; excellent visibility. The student had completed five touch and goes without incident. The student had performed very well with no apparent issues. This was the student's second supervised solo from this airport.The approach and landing to the sixth and final landing appeared normal with no notable variations. The landing flare appeared well developed with the aircraft landing on the mains in a nose high attitude. Upon initial braking the aircraft veered left with the left main wheel not in contact with pavement. Skidding and braking noise was apparent from my location approximately one hundred yards from the site. The aircraft partially departed the side of the runway in a nose and left main gear high configuration and rapidly stopped. The nose of the aircraft settled and I assume the prop strike happened at this time. The aircraft was only partially off the runway. The student had no apparent injuries and there was no apparent damage with the exception of the prop strike.The student later advised he was attempting to rapidly brake the aircraft so that he could exit at the first exit. It was during this rapid braking that the student lost control. Aircraft was parked and considered not airworthy and a report was filed.