A PA28 CFI MADE 3 SIGNIFICANT ERRORS WITH MRB TWR; CULMINATING IN LNDG WITHOUT CLRNC AT MRB.

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WHILE ON AN IFR FLT PLAN CONDUCTING A FULL PROC LOC BACK-COURSE RWY 8 CIRCLE TO RWY 26 APCH; 2 EVENTS OCCURRED: 1) WHILE PROC TURN OUTBOUND ON THE APCH; I ALLOWED THE PUI TO DSND 200 FT BELOW THE 'PT' ALT OF 3900 FT MSL. ATC ADMONISHED US FOR THE TRANSGRESSION. I RPTED WE WERE IN VMC THE WHOLE TIME AND THEY SAID VERY WELL UNDERSTAND VMC CONDITIONS/GND CONTACT. RPT 'PT'/FAF INBOUND. WE CALLED AT FAF AND SWITCHED TO MRB TWR. 2) STUDENT WAS FREAKED OUT OVER ALT CALL FROM ATC AND WENT 'DEAD IN THE HEADLIGHTS' WHEN TWR REQUESTED CIRCLE S L DOWNWIND FOR RWY 26. I TOOK CTL; CALLED THE CIRCLE COMMENCEMENT; WHICH WAS ACKNOWLEDGED BY TWR. STUDENT WOULDN'T SHUT UP ON DOWNWIND. DURING THE BABBLE; I FORGOT TO CONFIRM LNDG CLRNC WITH TWR. WE LANDED WITHOUT CLRNC. TWR ASKED 'DO YOU REALIZE YOU JUST LANDED WITHOUT CLRNC?' I APOLOGIZED AND TWR SAID 'NO PROB; SAY PARKING.' WE TAXIED CLR AT TXWY B. I HAD BEEN MONITORING TWR DURING THE ENTIRE 12 MIN APCH AND THERE WAS NO ONE ELSE TAXIING OR APCHING/DEPARTING. NO LOSS OF SEPARATION OCCURRED. CHAIN OF EVENTS: STUDENT HAD CRAPPY HEADSET AND COULD NOT HEAR 50% OF THE TIME/LOST ALT SITUATIONAL AWARENESS. WHILE I WAS CLRING FOR PT INBOUND; LOST SITUATIONAL AWARENESS FOR LNDG CLRNC. HUMAN PERFORMANCE: NEVER ATTEMPT TO FLY WITH A CREW MEMBER WHO CANNOT COMMUNICATE FULLY WITH YOU/ATC; IT IS A HUGE DISTR.