I have seen all the issues everyone has shared above in my DD's life - and my own (I spent most of my life with male friends, until I became a mother in my mid-30s).
No question that boys in the wrong environment are far more likely to wreak havoc in that environment; girls instead tend to tune out, shut down, or try to support the environment, such as by becoming the teacher's helper. Boys are much more likely to make their problem everyone's problem, and teachers are thus far more motivated to seek a solution. Girls put on the required public face and force their problems deep down inside - at least until they get home from school, where their families often see the damage and breakdown the schools never witness.
A good example of this in practice: our board uses CCAT (CoGat) or WISC to identify gifted students, which research shows should produce a 50/50 split. However, the major source of identification is teachers, so the gifted classes in our board are in fact 2/3 boys.
Girls really do learn terribly young that acting out is not tolerated for them, though it is expected in boys. Culturally, we push girls hard to compromise, fit in, help others and make them comfortable, and not make waves. There's some incredible disturbing research I'll try to track down in which teachers are given kids' profiles and asked for their opinion of the child's needs. With no change on the profile except a name, teachers were way more likely to identify a boy as likely gifted and needing more academic challenge, but a girl as a behaviour problem needing discipline. Ah - found it:
http://www.tandfonline.com/doi/abs/10.1080/02783193.2011.580500Honestly, it's not all on the teachers, either. I see in parents a tendency to expect the gifted girl to find a way to make it work, while they are more likely to seek a new environment for a gifted boy. Girls are expected to behave, and then they do behave, and then everybody, parents included, is less likely to see them as having severely unmet needs.
On the math side, I also watch, with great sadness, friends with a highly-gifted girl who loves Minecraft and coding as much as my DS, being pushed by parents into what they see as more appropriate pursuits. I do think many parents, in ways both subtle and overt, provide much stronger encouragement and support for boys in computer, engineering, science and math than boys. Mathiness in a girl is cute, and means she should do well in school. Mathiness in a boy tends to prompt a more proactive response, that results in parents taking them to math activities and contests at a young age. Most parents would be horrified, though, if you suggested they were doing this. Just like those playground studies that found parents swore they treated their kids the same, but in practice were way more likely to encourage boys but not girls to take risks and persevere at physically-hard challenges. I know I treat my DD very differently than her brother, and I am always worrying - am I responding to her total lack of interest in math - or have I inadvertently encouraged it? Even just thinking back to the noticeable differences in the toddler toy collections among friends houses when we all had our first babies... or the shockingly different ways people spoke to and handled my friends' mixed twins... the conditioning starts VERY young.
