SMA Y NON ADHERENCE TO ATC INSTRUCTIONS HAD NMAC WITH MTR. NMAC. SEE AND AVOID CONCEPT.

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OUR FACILITY IS A NON RADAR APCH CTL WITH APCH CTL LOCATED IN THE TWR CAB. I WAS WORKING LCL CTL WITH APCH CTL SEATED NEXT TO ME. I CLRED THE MTR FOR TKOF ON RWY 18 WITH A L TURN DIRECT THE VORTAC (LOCATED 2 MI NE OF THE ARPT) CLBING TO 4000 FT MSL. HE WAS PERFORMING A PRACTICE APCH SO I SWITCHED HIM TO APCH CTL. AT THE SAME TIME; I WAS WORKING IN 3 VFR SINGLE-ENG SMA'S FROM THE NE. AT THE TIME THE MTR BEGAN TKOF ROLL; I HAD 2 SMA'S IN SIGHT AND WAS ATTEMPTING TO LOCATE SMA Y WITH POS RPTS (SINCE WE HAD NO RADAR). HOWEVER; ALL 3 PLTS BELONGED TO A FLT SCHOOL LOCATED AT ANOTHER ARPT THAT TAUGHT NON ENGLISH SPEAKING FOREIGNERS AND WAS NOTORIOUS FOR SENDING THEM OUT WITH LIMITED NAVIGATION SKILLS AND EVEN MORE LIMITED ENGLISH. THEREFORE; THEIR POS RPTS WERE NEITHER MAKING SENSE NOR CORRESPONDING TO THE OBSERVED POS OF THE 2 IN- SIGHT ACFT. ALSO; THEY WERE NOT FOLLOWING INSTRUCTIONS; I WAS HAVING PROBLEMS SEQUENCING THEM AND I FELT ISSUING TFC WOULD BE USELESS AND CREATE MORE CONFUSION. APCH CTL ISSUED TFC TO THE MTR THEN OBSERVED SMA Y N OF THE VORTAC AT 3500 FT MSL; A FEW HUNDRED YDS FROM THE MTR HEAD-ON. APCH ISSUED AN IMMEDIATE R TURN TO THE MTR THUS AVOIDING A POSSIBLE COLLISION. I BELIEVE THE CAUSE OF THE INCIDENT WAS A COMBINATION OF THE LACK OF COMS BTWN THE 3 SMA PLTS AND MYSELF AND THE ABSENCE OF RADAR. EITHER ONE ALONE WOULD NOT HAVE BEEN SO DANGEROUS.