To increase opportunities for students to take more advanced math courses in high school, many school districts enroll grade 8 students in Algebra I, a gateway course for advanced math. But students who take Algebra I in grade 8 and skip other math courses, such as grade 8 general math, might miss opportunities to develop the foundational knowledge and skills required for success in advanced math courses. This leaves educators to determine which students are ready for Algebra I in grade 8 and which are not. To inform strategies that address this challenge, this study examined whether student knowledge in five math domains in grade 7 (ratios and proportional relationships; the number system; expressions and equations; geometry; and statistics and probability) was associated with Algebra I achievement in grade 8. [For the full report, see ED606821; for the appendixes, see ED606833; for the study brief, see ED606835.]