Researchers say that poor PISA test results by Swedish students may have been because of poorly-phrased questions rather than lack of knowledge by students.

After Swedish students performed poorly in the 2012 Programme for International Student Assessment (PISA) test in science there has been an urgency to reform the educational system in Sweden. But a new Swedish study now says that the reason for the bad results may lie more in how questions on the test were framed rather than student knowledge and skill.

Researchers filmed students while taking the test and say the evidence shows that students had difficulty understanding...