INSTRUCTOR WITH INSTRUMENT STUDENT TAXIES ONTO INTERSECTING RWY; CAUSES TKOF CLRNC CANCELLATION.

Narrative

AFTER AN UNEVENTFUL FLT MY STUDENT WAS VECTORED ON TO THE FINAL APCH COURSE FOR THE ILS. WE THEN SIGHTED THE RWY AND MADE OUR LNDG. WE WERE ROLLING OUT AND WERE INSTRUCTED TO TAXI CLR OF RWY AND CONTACT GND CTL. MY STUDENT SPOTTED A RWY INTERSECTION AND STARTED TO TAXI CLR. THE RWY WE WERE HDG TO WAS NOT IN USE AT THE TIME. IN THE MEANTIME; TKOF CLRNC WAS GIVEN TO AN ACFT WAITING SHORT OF THE RWY. AT THIS TIME MY STUDENT SAW A TAXIWAY FURTHER DOWN THE RWY AND STARTED TO TAXI ALONG THE RWY TOWARD THE TAXIWAY. THIS HAPPENED IN A VERY SHORT TIME FRAME AND I DID NOT HAVE TIME TO REACT TO GET US CLR OF THE RWY. THE TWR; HOWEVER; DID SEE THAT MY STUDENT ELECTED TO STAY ON THE RWY AND CANCELLED THE TKOF CLRNC. THE ACFT ON THE RWY THEN TAXIED CLR OF THE RWY AND RECEIVED TKOF CLRNC ON A PARALLEL RWY. THE WAY TO PREVENT THIS FROM OCCURRING AGAIN: 1) MORE ATTN SHOULD HAVE BEEN GIVEN TO WHAT WAS THE STUDENTS PLAN FOR EVERY SEGMENT OF THE FLT. INCLUDING THE LNDG. 2) THE TWR SHOULD NOT GIVE TKOF CLRNC UNTIL THE ACFT IS WELL CLR OF THE RWY AND SHOULD NOT ASSUME WHAT THE ACTIONS OF THE PLT WILL BE. IN SHORT; THERE SHOULD HAVE BEEN MORE EXACT COM BTWN THE TWR AND THE STUDENT AND MYSELF AND THE STUDENT.