A large part of the problem of underachievement is that boys are forced into a female model of learning. Schools teach and value oral communication and ideas represented on paper. The language and fine motor centres and of girls' brains have been shown to develop much earlier than in boys. This is not taken into account in the way that schools, particularly primary schools, teach. 
Michael Gurian's article written in 2006 talks about this in much more detail.  Michael is a researcher, author, and founder of The Gurian Institute, a respected organisation that has been trying to understand how boys learn. Helping boys to learn.