A brief update on this: FWIW, DD (6th grade) took the 7th grade state standardized math test per her acceleration and knocked it out of the park (from raw score, looks like she got all questions correct but one). So whatever is going on with algebra, she had no issues with 7th grade curriculum, at least as tested by the state. I still have a rather high degree of confusion regarding "8th grade math" and DD.