Students who think that a long sleep in on the day of a test is better for their grades may be shocked to find out that added rest could actually hurt a teen's marks, meaning they ought to spend less time in their double or single bed prior to doing their exam. A new study published in the Eastern Economics Journal discovered that more conventional wisdom may not necessarily be correct. Despite guidelines in the US - where the research was carried out - recommend nine hours of sleep a night, it may in fact be way too much. It was discovered by Eric Eide and Mark Showalter - economics professors at Brigham Young University - that students between 15 and 18 ought to target seven hours a night, following analysis of sleep and standardized test scores that existed before the study. The study also went on to show that the amount of sleep necessary for better grades generally declined with age - 16-year-olds were found to need around two hours less than ten-year-olds.