A Canadian professor gave students an early Christmas gift during finals week…accidentally.

Twas the final before Christmas, and all through the hall,
It seemed that a gift had been given to all.
For one professor had shared, along with the test, 
A partial list of which answers were best.

No, it’s not just a nightmarish twist on a holiday classic. It’s what happened recently at Ryerson University, in Toronto, when 190 engineering students in a required, intro-level chemistry course received final exams with part of an answer key on the back. An unnamed professor accidentally left a computer-generated key attached to one of the versions of the test, which was distributed to about one-fifth of students in the massive exam hall. The mistake meant those students had the first 20 answers to the 50-question exam.

Proctors realized the error within minutes, after a student quietly pointed it out. Immediately they asked all 1,000 students taking various versions of the exam to stop writing without explaining why. They scrambled to collect the keys by checking each exam book.

But the professors had to decide on the fly how to proceed. Should they cancel the exam, even though some 800 other students in the hall had different (answerless) versions of the exam? Should they dismiss only the students with the tainted tests, even though it was unclear how many had taken advantage of or even noticed the grading key in such a short period of time?

Ultimately, the proctoring professors decided to let the students proceed with all versions of the test, and analyze their responses later on to see if those who had received the keys scored unusually high marks on the first section of the test.

Days later – and perhaps much to the chagrin of those who had peeked at the key – students in the course received an email from their professors saying that the numbers indeed had been strange.

“Unfortunately, our analysis indicated that several students benefited from the answer sheet,” the email says. “Because of that, we have had to find a way to resolve the issue that is as fair as possible, under the circumstances, to everyone in the course, and maintains academic integrity.”