CPR SMT DESCENDED THROUGH THE ALT OF A FASTER; OVERTAKING MLG RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative

I WAS ASKED TO TRAIN A PERSON ON THE RADAR AT THE YOUNGSTOWN SECTOR WHICH I AGREED TO DO. THE SECTOR WAS STARTED TO GET BUSY SO THE SUPVR HAD THE TRNEE START TO WORK ON RADAR AT THAT TIME. MLG X AT FL210 WAS DIRECT TO YNG FROM THE NE. SMT Y AT FL220 WHICH WAS ON A TEST FLT FROM BKL ARPT TO ERI BACK TO BKL WAS ON ASSIGNED HDG 180 DEGS. WE WERE WORKING ABOUT 12 ACFT AT THIS TIME; NUMEROUS DEPS FROM CLE AND CLEVELAND SATELLITE ARPTS WERE COMING AT THIS TIME. THE TRNEE DSNDED SMT Y TO 15000'. I HAD GOTTEN DISTRACTED BY COORD THE D-SIDE CTLR WAS DOING WITH THE CLE DEP CTLR AND ADJACENT SECTORS AND INQUIRED WHAT COORD HAD TAKEN PLACE. WHILE DOING THIS I HAD MISSED THE XMISSION BY TRNEE DSNDING SMT Y. WHEN I REALIZED WHAT TRNEE HAD DONE I WAS UNABLE TO CORRECT HIS MISTAKE IN TIME TO PREVENT LOSS OF SEP SINCE MLG X HAD APPROX A 200 KT OVERTAKE ON SMT Y. KEEP IN MIND ALSO THAT THIS TRNEE IS ALREADY CHKED OUT ON 3 OTHER RADAR SECTORS SO IS NOT A BEGINNER. I FEEL THAT IF TRNEES WERE PUT IN SECTORS AT SLOWER PERIODS BEFORE THE SECTOR BECOMES BUSY AND THEN IS AFFORDED THE TIME TO BUILD UP TO THE BUSY PERIOD. DURING THIS SESSION THE TRNEE WAS TO BE JUDGED FOR CERTIFICATION. UNFORTUNATELY; AT MY EXPENSE; WE FOUND HE WAS NOT.