A C150 LANDS ON THE WRONG RWY DURING A TRAINING FLT. INSTRUCTOR PLT MISUNDERSTANDS THE CLRNC ON A RWY CHANGE.

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ON A STUDENT INSTRUCTIONAL FLT WE WERE N OF LFT ARPT. CALLED APCH TO ADVISE THEM WE WERE INBOUND TO ARPT FOR TOUCH-AND-GO LNDGS. CTLR ADVISED US TO 'ENTER L DOWNWIND; RWY 4L.' APPROX 8 MI OUT THE APCH CTLR STATED; 'ENTER L DOWNWIND; RWY 4L AND CONTACT THE TWR.' STUDENT CONTACTED TWR AND ADVISED INBOUND. TWR ADVISED; 'CLR TO LAND RWY 4R.' (THIS IS NOT CLR.) THE STUDENT READ BACK INSTRUCTION; 'CLRED TO LAND RWY 4R.' I THEN ASKED THE STUDENT IF WE WERE LNDG RWY 4R OR RWY 4L. HE REPLIED; 'YES; I MEAN RWY 4L.' I AM CERTAIN WE WERE CLRED TO LAND ON RWY 4L AND WE SHOULD HAVE REQUESTED CLARIFICATION; BUT DID NOT. THE CTLR DID NOT CHALLENGE THE RWY 4R READBACK. DURING APCH; TWR ISSUED TA TO ANOTHER ACFT AND ADVISED 'THERE IS A C152 ON FINAL TO RWY 4L.' TWR CTLR NEVER QUESTIONED OUR INTENTIONS UNTIL ROLLOUT AND TKOF THEN SAID; 'ACFT X; YOU JUST DID A MAJOR NO-NO; LNDG ON RWY 4L.' I FEEL RWY CONFUSION CAN BE REDUCED IF THE TWR WOULD REISSUE (ISSUE) 'CLRED TO LAND RWY XX' INSTRUCTION WHEN ACFT IS ON FINAL. I ALSO FEEL THE INCIDENT COULD HAVE BEEN AVOIDED HAD THE CTLR ASKED OUR INTENTIONS WHEN HE REALIZED THERE WAS A DISCREPANCY IN HIS AND OUR EXPECTATIONS. I WOULD ALSO LIKE TO SEE GREATER EMPHASIS WHEN THE TWR REVISED OUR LNDG RWY (IF IN FACT HE DID). THERE WAS NO CONFLICT WITH OTHER TFC; BUT IN A BUSY ENVIRONMENT; INCIDENT COULD HAVE HAD DISASTROUS CONSEQUENCES.