If you struggle in school, it's easy to believe that you're just not good at a particular subject. Studying, however, plays a significant role in predicting grades, according to a 2007 report by the National Bureau of Economic Research (NBER). Not all studying strategies are effective, however, and if you're using a strategy that doesn't work, you could be wasting your time.

Effectiveness of Studying

The 2007 NBER report tracked the performance of students who studied and those who did not. Unsurprisingly, students who studied received better grades than those who did not. Studying helps students move material learned from short-term to long-term memory, according to "Child Psychology" by Robin Harwood and colleagues. This makes it easier to apply information in novel contexts rather than just regurgitate it, and when students store information in long-term memory, they're more likely to excel on analytical tasks, such as essays.

Time Spent Studying

According to the 2007 NBER study, it's not the amount of time spent studying that predicts academic success but rather effective study strategies. While spending only two minutes studying for a complex class is unlikely to be effective, there is little evidence that grades correspondingly improve with more time spent studying. Anita Woolfolk emphasizes in her book "Educational Psychology" that some highly effective study strategies, such as reading a chapter twice and taking notes, tend to take longer than less effective study strategies. However, more time spent on ineffective study strategies is unlikely to increase grades.

Excessive Studying

A Journal of Experimental Education study points out that in some situations there may be an inverse correlation between studying time (measured in amount of hours spent on homework) and grades. The study found that homework taking two and a half hours or more to complete diminished the positive effects of studying and led to increased stress and declining health among students.

Students who struggle with a particular topic might spend more time studying, but they may continue to make poorer grades than students who "get" the subject matter. Students who've already mastered a subject may spend less time studying, so in some situations, time spent studying can indicate how much a student is struggling with the material.

Studying and Motivation

In his book, "Visible Learning," John Hattie analyzes several studies addressing education and motivation. He found that students with an intrinsic sense of motivation — those who believe that they affect the world around them rather than seeing themselves as victims of circumstance — tend to work harder and longer. This work ethic is also correlated with higher achievement. Students with an intrinsic motivation style will likely study as long as they need to master the material; for some, this could be a short period of time, while for others, the time could be dozens of hours each week.