THE INSTRUCTOR PLT (CFI) HAD NOT FLOWN A CESSNA 150K BEFORE & WAS ON HIS 1ST INSTRUCTIONAL FLT AFTER RECEIPT OF HIS CFI CERTIFICATE. THE STUDENT PLT HAD 9 HRS OF DUAL FLT TIME. THEY DEPD JEFFCO ARPT (BJC) AT 1855 MDT. AT 1900 MDT, THE BJC WX WAS IN PART: 12,000' SCT, 14,000' BKN, VIS 70 MI, WND 300 DEG AT 14 GSTG 33 KTS, TEMP 97 DEG, VIRGA IN ALL QUADS & TSTM ACTIVITY IN THE AREA. AFTER DEPG BJC, THE ACFT WAS SEEN ON AN APPARENT APCH TO A LARGE EMPTY PARKING LOT; THE APCH WAS THEN ABORTED. NO ENG PROBLEM WAS NOTED BY WITNESSES; THEY LAST SAW THE ACFT AS IT PASSED OVER THE CREST OF A HILL, DSCNDG ON A NORTHERLY HDG. IT CRASHED BYD THE CREST ON DSCNDG TRRN & WAS EXTENSIVELY DMGD. NO PREIMPACT PART FAILURE OR MALFUNCTION OF THE ACFT OR ENG WAS FOUND. THERE WAS EVIDENCE THE ACFT HAD ENCTRD MICROBURST ACTIVITY. APRX 15 MI SE AT STAPLETON INTL ARPT, MICROBURST ACTIVITY WAS RECORDED ON THE LOW LVL WND SHEAR ALERT (LLWAS) SYS. DENSITY ALTITUDE WAS ABOUT 9500'.