Like most other states, Missouri uses assessments intended to measure whether students are on a pathway to "college and career readiness." The state longitudinal data system now has the capacity to directly test that claim. We make use of 8th-grade assessment (MAP) scores in Math, Science, and Communication Arts for roughly 260,000 first-time Missouri freshmen who began high school between Fall, 2009 and Fall, 2012. These students were tracked through high school and for five years following on-time high school graduation. We find a strong positive association between MAP performance scores in 8th grade Math, Science, and Communication Arts and post-secondary college attendance and degree completion. This is true overall and for White, Black, and Hispanic students disaggregated by gender. Proficiency on all three exams matters even more. Based on a logistic forecasting model, if all students who scored below Proficient on the 8th-grade MAP raised their scores to Proficient, the number earning post-secondary degrees would increase by roughly 50 percent. Black and Hispanic students earning post-secondary degrees would increase by roughly 150 and 75 percent, respectively. We conclude that 8th-grade MAP proficiency scores are highly informative about whether students are on a pathway to college and career readiness.