File this story under “War on Men”.

As early as eighth grade, girls are more likely to say they want to go to college and to earn better grades in school because of it, a new study says.

The National Bureau of Economic Research working paper set out to account for a relatively recently widened gender gap in secondary school grade point averages. Looking at 8th- and 10th-graders and high school seniors, the researchers searched for correlations between G.P.A. and plans for the future, non-cognitive skills (social skills, motivation, etc.), the family environment, and working while in school.

One significant relationship emerged.

“There has been an important change in the vocational aspiration of girls that can explain a large part of the gender differences in their academic achievement,” said Nicole M. Fortin, a co-author of the study and professor at the University of British Columbia’s Vancouver School of Economics.

Those career goals translate into plans to attend college, which in turn prompt girls to do better in school than boys, the paper argues.

Although the gender gap in G.P.A. level for high school seniors has hovered around two tenths of a grade point (for example, 3.1 vs. 3.3 in 2009) for three decades, that has not historically translated into higher educational attainment or better labor market outcomes for women.

More recently, more high school seniors of both genders are earning As (presumably due to more grading on a curve, the authors posit), but girls are earning top grades even more often; from the 1980s to the 2000s, the difference between the proportion of girls and boys earning As nearly doubled, from 3.2 to 5.4 percentage points.

At the same time, the proportion of girls expecting to work a job requiring a postgraduate degree rose from 15.3 percent in the 1980s to 27.1 percent in the 2000s; for boys, it rose only from 13.5 to 16.4 percent. The authors argue it’s not a coincidence that during the same period, the percentage of girls expecting to work in a clerical job at age 30 fell from 21 to 3 percent — but that drop was not mirrored among boys expecting to work in skilled or semi-skilled jobs such as craftsmanship or protective services.

“There was a particularly sharp increase at the beginning of the 1990s where about a quarter of girls wanted to be in an occupation that might require a graduate degree,” Fortin said.