BUT.. fwiw, I'd take Sweetie's advice - sign up for the free 2-week trial verson of Aleks and have your ds take the assessments for as many grade levels as you can. The VERY USEFUL thing about the Aleks assessments is they will give you a detailed report that ties your child's knowledge to YOUR specific state curriculum standards (for all 50 states). It's also very easy to reset a grade level so that if your ds for instance, aces the grade level X assessment, you can switch him up to grade level X+1 and have him take that assessment (just be sure to save all the reports from the grade level X before making the switch).
The one gotcha with Aleks might be starting grade level - we used Aleks for after-schooling but it was several years ago, and at the time we used it, I think it started at grade 3.... but I also think they were adding in lower grade levels, or at least that was in their plan.
It still only starts at 3rd grade, *but* it splits things up into tiny topics and many of them are things that are taught before 3rd grade, e.g. "single digit addition with carry" is one topic there. So it still might be a good idea to try it out. My DS-then-5 did this straight from "write me a sheet of sums Mummy" and there was no bump. Doesn't help you document where he is against 1st or 2nd grade standards, but if he's likely to know (or very quickly learn) a non-trivial amount of the 3rd grade material that might do!
Unfortunately I don't think two-week free trials are easy to come by; the standard one only allows three hours of use, or something, and although longer trials specific to homeschoolers come round, you would have to claim to be homeschooling. One other gotcha: if you sign up for the free trial, and then purchase a subscription, the child gets the initial assessment again. I remember this upsetting my DS-then-5, for whom the 25-30 question initial assessment was a lot of concentration, and a lot of computer use given limited fine motor skills, at that time. If there's a decent chance you might actually use it, and if $19.95 doesn't stretch the budget too much, consider signing up for a month-by-month subscription instead, if you can't find a two week trial.
