By age four, girls believe they are better than boys.

[lumberjack_jeff]

http://www.parenta.com/2010/09/09/girls-boys-age/

Girls believe they are cleverer, better-behaved and try harder than boys at school from a very young age, new research has shown.

Such opinions are present from at least the time that girls are in their reception year, at the age of four or five, and persist throughout primary school.

Moreover, by the age of eight, boys appear to agree with their classmates, believing that girls are more likely to have what might be deemed the right qualities to do well at school. Children of both sexes also think that, in general, adults believe girls do better at school than boys.

The research, based on detailed questioning of 238 children in two Kent primary schools, was presented at the British Educational Research Association (BERA) conference on Thursday 2 September. It underlines the difficulties that teachers and educationists may face in trying to improve the performance of boys, who lag behind girls on average in most subjects throughout school.

[comtec]

1. Interesting... pity we can't teach that boys and girls are both capable

and stop teaching boys that being stupid is OK as long as they are good at sports...

As i've noted elsewhere, I hope all this is simply an over correction and we'll get back to where we need to be as a species, and teach both genders that they are both equally capable with potential.
while nit's true women tend to be better with language, males tend to be better with maths.

that is tends. there are plenty on both sides that are masters of language or mathematical geniuses.

[lumberjack_jeff]

2. Every September, almost every K-6 teacher I've talked to during open house...

... has complained about how difficult the upcoming year will be based on how many boys are in her class.

Of course the students get that message.

[comtec]

3. We adults think kids don't hear things like that

But I do remember hearing stuff like that when i was a kid, and understanding.
it's a pity that's how things are.
Granted, it's also a pity that's how young boys can be in class too.
I wonder if it's to do with genetics (boys feel the need to run around like maniacs) or breeding (girls are taught to sit and be quiet)

[JonLP24]

4. That is the way society conditions us

From very young ages, boys and girls and raised differently. The running around is attributed to "boys will be boys". I can think of countless other examples but it affects us in life. One way I can think of is breakdown in communication in marriages or relationships. One way is women growing up where encouraged to express and share their feelings while men where told to "suck it up". This is why sometimes men will use anger to cover feelings of sadness or fear. Hope I'm making sense. Wish I still had that book but I was trying to answer your question. Society and our parents condition us to believe we're different in those senses.