INSTRUCTOR FLIES WRONG TFC PATTERN; NOT CHALLENGED OVERTLY BY ONT LCL CTLR; BUT RECOGNIZED BY STUDENT.

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I WAS DOING A NIGHT XCOUNTRY WITH A PVT PLT STUDENT FROM SNA DIRECT BUR DIRECT ONT TO SNA. ON OUR WAY TO ONT; SOCAL HANDED US OFF TO ONT TWR AND WE WERE TOLD TO MAKE L-HAND TFC FOR RWY 26L AND THAT A BRASILIA WAS ON FINAL FOR RWY 8; OPPOSITE DIRECTION. I WAS NOT WORRIED BECAUSE WE SAW THE TFC LNDG ON THE L RWY AS WE WERE ENTERING ON A 45 DEG. I COMMENTED TO MY STUDENT HOW TIRED I WAS AND LOOKING FORWARD TO ENDING THE FLT SOON. WE THEN CONTINUED TO LNDG WITH NO UNUSUAL HAPPENINGS. (SO I THOUGHT.) WE THEN TAXIED FOR DEP FOR 1 TURN IN THE PATTERN. WE DEPARTED THE RWY AND MADE R CLOSED TFC. ON SHORT FINAL; I CALLED UP THE TWR FOR OUR LNDG CLRNC TO CONFIRM THE RWY. THEY RESPONDED THAT WE WERE CLRED TO LAND ON RWY 8L; BUT WE WERE LINED UP ON RWY 8R! I TOLD THIS TO ONT TWR AND WAS GIVEN CLRNC TO LAND ON RWY 8R. WE THEN LANDED AND THEN TAXIED FOR DEP TO SNA. WE THEN DEPARTED ONT AND LANDED AT SNA WITH NO FURTHER OCCURRENCES. AFTER LNDG AT SNA; I DEBRIEFED MY STUDENT ON WHAT HAD HAPPENED AT ONT. TURNED OUT THAT ON INITIAL CONTACT WITH ONT TWR; WE WERE TOLD TO MAKE L TFC FOR RWY 8L; BUT WE MADE R TFC FOR RWY 8R. MY STUDENT NOTICED THIS; BUT DID NOT QUESTION OUR ACTIONS AND ONT TWR NEVER SAID A THING. WE ENDED UP LNDG ON RWY 8R INSTEAD OF RWY 8L (OPPOSITE DIRECTION OF THE BRASILIA). ONT TWR STILL SAID NOTHING. WHEN I ASKED MY STUDENT WHY HE DIDN'T SAY ANYTHING; HE SAID HE THOUGHT I KNEW WHAT I WAS DOING. FACTORS LEADING UP TO THIS RWY INCURSION WERE FATIGUE (MINE AS THE INSTRUCTOR); AND COMPLACENCY (MINE; MY STUDENT'S AND ONT TWR'S). IF I HAD GOTTEN MORE REST; OR IF MY STUDENT OR ONT TWR HAD SAID SOMETHING; THIS COULD HAVE BEEN AVOIDED. FROM NOW ON; I WILL MAKE SURE I GET ENOUGH REST BEFORE NIGHT FLTS AND HAVE TOLD MY STUDENTS THAT IF SOMETHING IS WRONG OR SEEMS WRONG; TO SPEAK UP. AFTER ALL; NONE OF US ARE PERFECT.