AN ACFT DEPARTS SNA WITH AN IMMEDIATE TURN RESULTING IN ANOTHER ACFT BEING OVERFLOWN BY 50 FT.

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I EXPERIENCED AN NMAC WHILE OPERATING AS A FLT INSTRUCTOR CHKING OUT ANOTHER INSTRUCTOR IN AN ACFT. THE NMAC OCCURRED WHILE I WAS PERFORMING AN ENG RUN-UP IN ACFT #1 AT THE MIDFIELD RUN-UP AREA AT SNA. THE MIDFIELD RUN-UP IS LOCATED JUST E OF THE DEP END OF RWY 19L. ACFT #1 WAS PARKED ON A HDG OF APPROX 010 DEGS WITH RWY 14/19L IN FULL VIEW OVER THE NOSE. I FIRST NOTIFIED ACFT #2 JUST AFTER IT HAD LIFTED OFF FROM RWY 19L. ACFT #2 TURNED TO THE L IMMEDIATELY AFTER LIFTOFF AND FLEW DIRECTLY AT ACFT #1. ACFT #2 THEN FLEW OVER ACFT #1 AT AN ALT OF LESS THAN 50 FT. MY STUDENT AND I ESTIMATE THE ALT OF ACFT #2 TO HAVE BEEN EQUAL TO 1 WINGSPAN JUST BEFORE IT FLEW OVERHEAD. THE CEILING IN ACFT #1 IS TRANSPARENT; AND I COULD MAKE OUT PART OF THE CALL SIGN OF ACFT #2. I COULD ALSO MAKE OUT A SYMBOL PAINTED ON THE VERT STABILIZER. THE SOUND OF ACFT #2'S ENG WAS ALSO CLRLY HEARD OVER THE ENG NOISE IN ACFT #1; WHICH WAS AT 1000 RPM AT THE TIME. HOW THE PROB AROSE: ACFT #2 WAS PRACTICING TOUCH-AND-GO LNDGS; THEY DID NOT LIFT OFF OF THE RWY UNTIL APPROX 500 FT SHORT OF THE END OF THE RWY; THIS ACCOUNTS FOR THE VERY LOW ALT. CONTRIBUTING FACTORS: ACFT #2 TURNED L BEFORE REACHING A SAFE ALT. IT IS STANDARD PROC AT SNA TO OFFSET THE UPWIND 15 DEGS TO THE L; HOWEVER; THIS SHOULD BE DONE ONLY AFTER REACHING A SAFE ALT TO CLR OBSTACLES; AND OTHER ACFT BY A SAFE DISTANCE. HOW IT WAS DISCOVERED: I HAVE SEEN ACFT #2 MAKE THE L TURN IMMEDIATELY AFTER TKOF SEVERAL TIMES OVER THE LAST 6 MONTHS; BUT I WAS NEVER UNDER THEIR FLT PATH BEFORE. IN THIS CASE; I WAS DIRECTLY UNDER ACFT #2 AND I FELT THAT THEIR ACTIONS PUT ME AT RISK. CORRECTIVE ACTIONS: ACFT #2 IS USED FOR FLT INSTRUCTION BY ONE FLT INSTRUCTOR. THIS FLT INSTRUCTOR NEEDS TO BE INFORMED THAT THIS TYPE OF FLYING NOT ONLY PUTS HIS STUDENTS AT RISK; BUT IT PUTS PLTS AND PAX OF OTHER ACFT AT RISK AS WELL. THESE OTHER ACFT INCLUDE THE AIRLINERS THAT TAXI DOWN THE TXWY A JUST BEHIND THE MIDFIELD RUN-UP.