DD did pre-algebra as independent study over the summer prior to enrollment in algebra as a 7th grader. She's never had any trouble at all, and believe me, we definitely treated the material rather desultorily during that summer; I basically had her run through the homework helper end-of-chapter tests on Pearson's website, and she got 90% or better on all of them, so I called that good.

Schrödinger's cat walks into a bar. And doesn't.