To get back to the original question, all elementary (and middle school) Aleks levels seem to pile up the new stuff on top of everything else that was included in the previous level.
Because I have slightly obsessive tendencies...
LV3 has 127 subjects.
LV4 has 198 subjects, 71 are new, 127 repeated from LV3 (64% repeated material, yes, all of LV3 is in there)
LV5 has 267 subjects, 69 are new (74% repeated material, ditto)
LV6 has 325 subjects, 58 are new (82% repeated material, ditto)
Yannan, if your daughter is at 48% of LV4 she is 1) appropriately placed (>25%, <85%) per Aleks suggestions but 2) probably not halfway through 4th grade math but more likely 2/3rd of the way through 3rd grade math (give or take a few things).
+1 everything DeeDee and ColinsMum said. Aleks per se is *not* a complete math program, and having kids zoom ahead can create issues. Not enough instruction, questions too narrow/similar to teach and test deep comprehension of concepts.
We still like it, but you have to understand the flaws.
