He's in third grade. Things definitely excite him (Legos, minifigs, comic books, drawing out his own comic books, video games, playing chase with a nerf gun with the other boys). He's just not that interested in working hard to do what they want him to do at school in the interest of people-pleasing.
From what I remember he has quite a split between this 'intellectual' subscales and his 'handmaiden' subscales - so for him, performing above average at school has a super high cost that your daughter doesn't have.
I would encourage him to get as much out of the activities that already interest him - particularly the comic books, legos,minifigs...conventions if they are nearby enough, comic books about the minifigs, blogs about legos and
http://www.google.com/products/catalog?hl=en&sugexp=pfwl&tok=tjFOSrVyBMvyDWjfyxtHbw&cp=14&gs_id=15&xhr=t&q=forbidden+lego+book&biw=1024&bih=567&gs_upl=&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&wrapid=tljp1326833530525025&um=1&ie=UTF-8&tbm=shop&cid=634997623327876615&sa=X&ei=ft8VT7yOEIXy0gGX1MiyAw&sqi=2&ved=0CEAQ8wIwAQ#
As 'average' as his Working Memory is, and his processing speed, he is really going to have the 'straight and narrow path' of doing what he finds internally motivating.
So do your afterschooling with a lego theme, and bribe with Lego-related activities.
such as -
http://www.firstlegoleague.org/best wishes,
Grinity