Malek Abu-Jawdeh and Shwetlena Sabarwal took on this very issue in a blog post in 2017. In it, they explore the gaps in myths and perceptions about gender. These gaps have existed at least since the Victorian era. The question is are any of them true?

Girls outperform Boys on test averages. Data shows that boys lag behind girls on internationally benchmarked test averages. “Whether on Latin America’s TERCE, the SAT and the NAEP in the United States, or an array of national and regional assessments around the world, girls outperform boys on total test averages in the majority of countries and economic regions.” Behind the averages, however, is a more complex story. At the top of the distribution of scores boys outperform girls, and they underperform at the bottom. In fact, 6 out of 10 underachievers across the OECD countries who fail to meet the baseline standard of proficiency, are boys. Boys are also more likely than their female counterparts to repeat a grade, they are less likely to pursue college, and less likely still to persist in attaining a degree if they do go to college. “Despite this higher performance by women, female college students continue to be underrepresented in technical fields like engineering and computer science.”

Gender-based gaps emerge early on and grow over time. While boys and girls tend to perform equally in both mathematics and reading scores up to second grade, starting in third-grade boys begin scoring slightly better in math and worse in reading. This particular gap continues to grow through elementary and middle school. The gap may be shifting, however, as there has been evidence in some countries that girls are closing this gender gap and demonstrating fewer statistical differences in gender performance in math and science

Is it Nature or Nurture? Nature may play a role, as boys have larger brains on average but girls’ brains mature more quickly. Additionally, the hippocampus (responsible for memory and language) is larger in girls and develops more rapidly. “Girls also have more of their cerebral cortex defined for verbal function which impacts vocabulary reading and writing. Boys, however, have more of their cerebral cortex defined for spatial relationships.” Girls tend to be calmer, and interested in emotional connection due to a higher production of serotonin and oxytocin. This also allows them to maintain focus for longer periods of time. Nurture also plays a role, because teachers tend to show a bias in how they engage boys and girls in the classroom. There is evidence that suggests that teachers tend to praise comments made by boys while only acknowledging comments from girls. Teachers also seem to have a different expectation of academic performance from boys than they do girls.

So are girls smarter than boys? I encourage you to read this article in its entirety https://blogs.worldbank.org/developmenttalk/are-girls-smarter-boys so that you are able to make your own informed decision.