Everyone who has been to school knows about bringing standard No. 2 pencils to exams. A head full of knowledge is a big help. But new research suggests students who take a drink have an edge over those who don’t. (A drink of water, that is.)

Psychologists at the University of East London and the University of Westminster did the study that suggests students who take water to drink while they take exams may improve their grades.

The study didn’t determine why that is. Chris Pawson, of the University of East London’s School of Psychology, said it might be that students keep themselves hydrated. Or, he says, it might be that drinking water helps reduce anxiety, which can adversely affect performance.

The study took into account students’ other grades in an effort to rule out the possibility that more able students are more likely to take water into exams.

Dr. Pawson says there is more study to be done. For example, is there a difference between the performance of those who drink water and those who simply take it with them?

But until that is determined, educators have their own question to answer. When they pass out blue books, shouldn’t they pass out bottled water too?