It hurts underperformers. https://jhr.uwpress.org/content/50/1/159 https://jhr.uwpress.org/content/50/1/159 >We find no evidence of a positive mean impact of

It hurts underperformers. https://jhr.uwpress.org/content/50/1/159 https://jhr.uwpress.org/content/50/1/159 >We find no evidence of a positive mean impact of acceleration in any specification and significant negative effects on performance in both Algebra I and the traditional followup course, Geometry. Accelerating algebra to middle school appears benign or beneficial for higherperforming students but unambiguously harmful to the lowest performers. We consider whether the effects reflect the reliance on less-qualified teachers and conclude that this mechanism explains only a small fraction of the result. Anecdata, fwliw: I learned multiplication and division in preschool, and I still loathed math to the point of neglecting it later (maybe because of how hellish math kept on being through 1st and 2nd grade overseas). I didn't even fully understand fractions when I took the SAT. (I'm just lucky my reading/writing were stellar. ;) (So that I could go on to fail both calc 1 and 2 when taking CS in uni. Made it through the second time though, mwahaha!)