Books are tricky since the required funding/publicity tends to mean that only people with reactionary/highly-conservative viewpoints can break into that, and come with their own views on why we have this gap and how to address it. Mostly this is something you'll find in academic articles and published statistics.
The US Department of Education's June 2012 report on gender equity is a decent starting point:
What you'll find there is that the conventionally-assumed narratives don't hold; there's a lot more parity in enrollment for higher-level courses including sciences and many maths courses (and sometimes even a gap in the unexpected direction, as with girls outnumbering boys in AP science courses), for example. Girls are also more likely (and have been more likely for nearly 40 years) to be enrolled into programs for gifted/talented students, while boys are nearly 1.5 times more likely to be held back and forced to repeat a grade.
Judith Kleinfeld (University of Alaska, Fairbanks) has written a few articles -- though fully-cited and sourced versions are hard to find free -- arguing that a major component of perceived gaps in performance may also be from greater variability in boys; focusing only on achieving parity at the highest levels of achievement has meant that boys' original overrepresentation at the lowest levels has not only persisted but grown, and remains unaddressed.
A study at the University of Georgia published this year looked into why girls receive higher grades and lower standardized-test scores.
Girls and boys both persistently believe that girls "are cleverer, better-behaved and try harder than boys at school".
And that's really just the tip of the iceberg. But like I said, spend some time searching on relevant terms and you'll turn up a lot of research that may make you question what "everybody knows" about gender and education.
The US Department of Education's June 2012 report on gender equity is a decent starting point:
http://www2.ed.gov/about/offices/list/ocr/docs/gender-equity...
What you'll find there is that the conventionally-assumed narratives don't hold; there's a lot more parity in enrollment for higher-level courses including sciences and many maths courses (and sometimes even a gap in the unexpected direction, as with girls outnumbering boys in AP science courses), for example. Girls are also more likely (and have been more likely for nearly 40 years) to be enrolled into programs for gifted/talented students, while boys are nearly 1.5 times more likely to be held back and forced to repeat a grade.
Judith Kleinfeld (University of Alaska, Fairbanks) has written a few articles -- though fully-cited and sourced versions are hard to find free -- arguing that a major component of perceived gaps in performance may also be from greater variability in boys; focusing only on achieving parity at the highest levels of achievement has meant that boys' original overrepresentation at the lowest levels has not only persisted but grown, and remains unaddressed.
A study at the University of Georgia published this year looked into why girls receive higher grades and lower standardized-test scores.
Summary: http://news.uga.edu/releases/article/why-girls-do-better-in-...
Full article (subscription required): http://news.uga.edu/releases/article/why-girls-do-better-in-...
Their findings indicated a persistent grading gap in favor of girls, based on behavioral rather than academic factors.
In the UK, research pointed to expectations and stereotypes as a source for the gap:
http://www.kent.ac.uk/news/stories/girls-believe/2010
Girls and boys both persistently believe that girls "are cleverer, better-behaved and try harder than boys at school".
And that's really just the tip of the iceberg. But like I said, spend some time searching on relevant terms and you'll turn up a lot of research that may make you question what "everybody knows" about gender and education.