STUDENT IN CESSNA 152 (N93748) WAS SEQUENCED TO LND BHND N97M AS BEECH 90 (N20) WAS AWAITING TKOF. AS N97M WAS LNDG, N20 WAS CLRD ON RWY TO HOLD & THE STUDENT WAS CLRD TO LND. 39 SEC LTR, N20 WAS CLRD FOR TKOF. SHORTLY THEREAFTER, N93748STALLED AND CRASHED APRX 580' SHORT OF THE RWY. WITNESSES SAID THE STUDENT FLEW FM A CLOSE BASE TO A SHORT FINAL APCH, THEN MADE 2 OR 3 STEEP S-TURNS AT LOW SPEED, AS IF TO GET MORE SEPN BHND N20. TOWER SUPVSR (CIC) OBSERVED INADQT SEPN BUT TOOK NO ACTION TO CORRECT IT. WITNESSES SAID N20 WAS HOLDING ON THE RWY WHEN THE STUDENT BEGAN S-TURNING. BFR TKOF, THE PLT OF N93748 TOLD GND CTL SHE WAS A STUDENT. THIS INFO WAS NOT PASSED TO LCL CTLRS. LCL CTLR WAS IN TRNG. NEITHER HE NOR HIS INSTRUCTOR KNEW THE PLT OF N93748 WAS A STUDENT. AIM RCMDD STUDENT ID ON INITIAL CALL TO RDO FAC. BUT, ATC HNDBK DIDN'T REQUIRE INFO TO BE FWDD. FLAPS WERE FND AT 10 DEG; STUDENT WAS TRND TO USE FULL FLAPS AND USE S-TURNS ON FINAL FOR SPACING, AND TO RAISE FLAPS FULL UP FOR GO-ARND; POH RCMDD 20 DEG OF FLAPS UNTIL SAFE SPEED WAS OBTAINED.