We've used ALEKS this year for 5th grade and it's working out great for us. My daughter spends 30 minutes per day on it, and she's already almost finished meeting the standards for 5th grade. I believe they will automatically start the next level when you finish the current one. If your student is not self-motivated, this may not be the program for you. I tried it with my 3rd grader, using the free one-month trial, and it didn't work out at all because at this point she really needs Mom right there with her when she does her work. I'll probably try it again for her later on.
There are times when the explanations aren't enough for my dd, and then she and I work it out together--this happens a couple of times a week. I recommend you use the free trial, and see if it's a fit for your family.