Using the High School Longitudinal Study of 2009, we examine the association between taking Algebra I by the eighth grade and students' later achievements and advanced mathematics course-taking. To explore our research questions, we employ three distinct methods--regression analysis, fixed effects models, and propensity score matching. In all our analytic models, we consistently found that students who have taken Algebra I by the eighth grade are more likely to have higher achievements in the ninth and eleventh grades and to take classes beyond Calculus during high school. Although the study is correlational, considering the increasing number of students taking Algebra I by the eighth grade, its findings have meaningful implications for education policy, research, and practice.