Our experience is that for a child who finds ALEKS motivating, it can become a problem to let them get too far out of the level where they are working at school. Our DS was 5 years/grades out of sync with age peers; we recently pulled the plug and stopped giving him ALEKS math, but in the meantime there is no sensible class to put him into, because he knows most (but not all) of what's covered in several different grades.
I think it's fine as a supplement, but it's not a replacement for math instruction, and I've seen a real downside in letting a kid work as far ahead as he can.
DeeDee
