A C150 EVADED A C172 ON A CTAF ARPT RWY WHEN THE C172 LANDED THE WRONG WAY.

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A GUSTY DAY AT SCAPPOOSE INDUSTRIAL AIRPARK FOR ME AND A PVT PLT. WE WERE DOING TOUCH AND GOES. WE WERE MAKING REGULAR RADIO CALLS AND BEING ESPECIALLY VIGILANT FOR COLLISION AVOIDANCE; AS IT WAS SO ACTIVE. WE HAD JUST LANDED AND MY STUDENT APPLIED FULL PWR FOR THE DEP WHEN I NOTICED WHAT APPEARED TO BE THE STROBES OF AN ACFT DEPARTING. HOWEVER THIS WAS NOT THE CASE AS THE PLANE GOT CLOSER TO US VERY QUICKLY UNTIL WE WERE BOTH REQUIRED TO TAKE EVASIVE ACTION ON EDGES OF THE RWY. THE OTHER PLT APPEARED TO TAXI OFF TO A REMOTE CORNER OF THE RWY IN HOPES OF AVOIDING CONFRONTATION WITH US. HOWEVER; WE FOUND HIM AND HIS PAX AND INQUIRED ABOUT HIS UNUSUALLY UNSAFE AND RECKLESS PATTERN ENTRY. HE CLAIMED THAT THEY FORGOT TO TURN THE VOLUME UP ON HIS RADIO AND THEREFORE DID NOT REALIZE THAT EVERYONE WAS LNDG IN THE OPPOSITE DIRECTION. AS AN INSTRUCTOR; I HAVE NOTICED MANY OCCASIONS WHERE CONFUSION EXISTS AROUND CORRECT PATTERN ENTRY AND COLLISION AVOIDANCE AROUND THE ARPT. THERE MUST BE A GREATER EMPHASIS ON THIS SUBJECT DURING PRIMARY TRAINING.