In case it is helpful to anyone, I wanted to say that my DS8 (2nd grade) has been using aleks to replace math at school for about 2 weeks. So far it is working really well. At first I think it was a bit of a distraction for the other kids (curious about what he was doing), but that has settled down now and I guess the other kids just mostly ignore it. He started on 6th grade, but finished it in the first week. He is now doing pre-algebra and is about 75% finished.
As far as how they will determine grades for him, I believe they will still grade him on mastery of grade level stuff, but I have been forwarding the weekly reports that aleks sends me - shows how much time he spent working, what topics he mastered, etc. Seems this could be used for a grade if they wanted to.
We could also print homework from this, but the teacher said they were fine if I just signed that he did 1/2 hour of work online in the evening to replace math assignments (he would normally have math worksheets 2x/week). 1/2 hour is more than he would spend on the easy stuff they would send home, but he enjoys aleks and wants to spend more than 1/2 hour anyway and really hated the normal busy work.
My main concern was whether he should be doing something more challenging than aleks since he is moving through so quickly. I asked our family consultant (from DYS) about this. She said if he is happy with it and it is working well for school and home, I shouldn't worry about it for now. So, I am going with that opinion at this point. When he finishes this class, he should be ready for algebra. I believe aleks goes all the way up through many high school level classes.