A teacher in the eastern Polish city of Bialystok gave the size of a boat and the number of people on board.
The students' assignment? To calculate how many Syrian refugees had to be thrown overboard for the boat to stay afloat and reach Greece.
The teacher, Grzegorz Nowik, said it was a matter of holding the students' attention.
"Pupils are not interested when I explain the lift of a wooden block floating on water," he said. "I told them it was a joke while saying words to be written down."
Mother: 'I am at a loss for words'
But if it was a joke, it was to many people a tasteless one, coming as it did when families trying to escape the war in Syria are drowning on a regular basis.
And one mother, upon seeing the assignment in her daughter's notebook, was not amused. She photographed the assignment and posted it on her Facebook page.
"4 refugees from Syria are to reach Greece on a raft which is 1m x 2 m x 20cm and (illegible) 800kg/m2," the assignment said. "Calculate how many refugees you need to push off the raft for them to reach their goal if each of them weigh 60kg."
"This is the assignment made by a public schoolteacher in Białystok," the mother wrote, according to Sputnik News, an official Russian news agency. "I am lost for words trying to comment on this."
School officials: If repeated, teacher will be fired
School officials did not appreciate the joke, either.
"We will terminate our cooperation immediately if it happens again," said Elzbieta Stasiewicz, deputy director of the Bialystok Gymnasium. "The teacher apologized and repented for what he had done."
And the assignment drew criticism as well from Anna Mierzynska, of the Normal Bialystock Association, a group that promotes acceptance of multiculturalism.
"This test question has some kind of subtext, not expressed directly -- how many people must die so that anyone could survive," Mierzynska said. "This is question about murdering."