High school girls are leaving boys behind, and it’s because girls are simply setting their sights higher, if a new study is correct.

Many psychologists believe that students set expectations and goals for their educations and careers early on, and then put in the amount of work required to meet those expectations during high school. Students aiming to be professionals or academics are more likely to strive for A’s, while other students planning on careers that demand fewer educational credentials are more willing to settle for B’s and C’s.

In a National Bureau of Economic Research paper released Monday, three economists suggest that high school girls’ rising expectations for themselves have translated to more girls getting A’s. The mode of girls’ GPA distribution has risen from a B to an A from the 1980s to today, while it’s remained at a B for boys.

The biggest factor in the rise in girls’ high school achievements has been the increase since the 1970s in the number of girls who plan to attend graduate school, the authors conclude. They write that their findings “show that the predominance of girls at the top of the GPA distribution is rooted in their higher educational expectations, themselves linked to career plans that include a graduate degree (such a law or medical degree).”

Meanwhile, boys’ expectations have not shifted as quickly in part because boys plan on entering male-dominated occupations that do not require higher education, the authors explain. More boys are likely to plan on going to vocational school or military service rather than go to graduate school. The authors note, however, that disciplinary problems are also likely to drag down boys’ grades in high school.

The study was written by Nicole Fortin of the Vancouver School of Economics, Philip Oreopoulos of the University of Toronto, and Shelley Phipps of Dalhousie University. The three economists used data from the Monitoring the Future surveys conducted by the Institute for Social Research at University of Michigan to illustrate education trends.