Large Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 7
Training / Qualification; Situational Awareness; Confusion; Distraction
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors; Procedure
I was the instructor providing OJTI at sector 21. I had not trained with developmental in a week or two and was told he was ready for certification. Faster jet traffic was climbing out behind Aircraft Y traffic on the ZMBRO departure. Aircraft Y's final altitude was FL230 and they were cleared to it. Developmental 'Got higher' for the Aircraft X jet to make sure they kept climbing through FL230 and did not level. As Aircraft X was approaching FL230 climbing he transferred communications to the next sector before ensuring separation. I did not react fast enough and could not stop the frequency change. The next sector issued a slight turn and Aircraft X ended up topping Aircraft Y by 1000 FT with not much room to spare.  Always make sure you are ready to step in as an instructor and take the frequency. Your developmental may just do the dumbest thing possible at any time. A turn further to the right should have been issued to Aircraft X jet sooner and none of this would have been a problem.
ZMP Controller while instructing has an aircraft climbing faster than previous aircraft; Developmental gives higher for faster climbing aircraft. Developmental transfers communication on faster climbing aircraft before separation is ensured.