In an effort to make sure that the 9 year old boy isn't playing catch-up as much as his sister, I've signed him up for Aleks.com's math program. It is an online math tutoring program that I found mentioned on several home schooling and parent websites. It starts with a 30-question evaluation of what the student knows.
I gave the boy, who is going into 4th grade, the 3rd grade evaluation. I wasn't entirely surprised, but I was entirely disappointed, that he only scored 55% on the test. That means he knows 55% of what he should--and that is comparing his knowledge to the California standards (we live in Los Angeles.) He was okay with the basics, but weak in geometry and fractions. His math program is philosophically opposed to teaching long division, so he will need some work with that, and his sister hasn't really been taught unlike fractions either, or division of fractions. Aleks, I hope, will fill in the blanks.
I gave his sister the 6th grade test (she's going into 6th and has been getting a great deal of tutoring in the last 6 months) and she scored a 71% on it--not bad. She already knows 71% of this year's curriculum and school doesn't start for a few days yet.
So, I will be using Aleks for him and not for her.