A More Difficult Test

Once right before a final, the professor declared that he would be leaving the room for the duration of the test, and returning in two hours, the amount of time the students were allowed for the final. He stipulated that they were not allowed to leave the room until the professor had returned, regardless of when they each completed the final.

The students were incredulous. But, just as he had stated, the professor handed out the tests and left the room, shutting the door behind him. The students waited a few moments, to be sure the professor would not barge in, and immediately began collaborating and cheating on the final. They shared notes and answers, got out their books, and began really laying into the test.

After two hours or so, the last student finally turned his paper face down. The professor came in shortly afterward, and declared that everyone had failed the test. He left, and the students all sat in their chairs, stumped.

Little did the students know that the professor had built a private study room for himself right behind the classroom, and had put a one-way mirror in between the two rooms. He had left the room and simply walked into his private study, sitting there and gleefully watching his little experiment unfold. The professor had decided before giving the test that any student who did not cheat and take advantage of the professor's "absence" would be given a 100% on the test, regardless of what his or her actual test score might have been. However, all those that he saw cheating would be given a zero.

As he had predicted, and very unfortunately for them, the students took full advantage of his absence. Every single one of them failed the final.