"Year-round Schools don't Boost Learning, Study Finds": A ridiculous test

"Year- round Schools don't Boost Learning, Study Finds" reads the title of an article in Science Daily. It is about a study done by Ohio State sociologist, Paul von Hippel, that tested children's reading and math skills. Half of these kids went to year-round school, and the other half went to traditional school. The skills of the year-round school children and traditional children were compared and von Hippel came to this conclusion; " We found that students in year round schools learn more during the summer, when others are on vacation, but they seem to learn less than other children during the rest of the year." That is such an ignorant conclusion. Is he trying to say that in year-round schools the teachers drill kids with information only in the summer, and then lay off the rest of the year? I doubt that is how the year-round school teacher work. To say learning is not boosted by year-round school, by the means of this study, is not reliable.