With respect to your recent long, well-documented but totally misleading piece on sexism in education, I must again offer the contrary evidence. Your point--and the point of the gender-in-education people--is that girls are lower achievers educationally because teachers (and other adults) provide lower expections, indeed a recognized factor. But this approaches absurdity on its face. If so we would have to postulate an amazing, unenforced, worldwide conspiracy in education and home-training.
But the biological basis, which you dismiss as merely controversial, was adequately explored by British biologist Corinne Hutt in 1972. She found that girls develop faster than boys in every way and that they are thus more ready than boys for specific learnings at given ages. They are ready for "numbers," she says, at 4 but are held back to get them in regular "unisex" teaching at 6.
This finding becomes critical in the light of Maria Montessori's basic work of nearly a century ago. Montessori identified "critical periods," later to be so well explored by the ethologists, for specific learnings. If a critical period is passed over without the indicated exposure, she noted, the child may suffer a permanent deficit in that learning element.
Hutt opines that failure to expose girls to numbers on time is responsible for the frequent lifelong female math deficit. Some return to education is therefore indicated, she adds.