As an educational intervention, acceleration is decidedly effective for high-ability students. The research support for acceleration that has accumulated over many decades is robust and consistent and allows us to confidently state that carefully planned acceleration decisions are successful. Both grade-based and content-based acceleration are effective interventions in academic and social-emotional domains for high-ability students. Grade-accelerated students generally outperform their chronologically older classmates academically, and both groups show approximately equal levels of social and emotional adjustment. To be clear, there is no evidence that acceleration has a negative effect on a student's social-emotional development. (Contains 3 endnotes.)