In the 2014-15 school year, 47 states are administering high school assessments to gauge students' mastery of college and career readiness standards in English language arts (ELA) and math. These new assessments represent a departure from prior high school exams that measured acquisition of high school (or lower) content but provided no actionable metric of a student's college and career readiness. This ECS Education Policy Analysis delves into statewide high school college and career readiness assessments and how states are using them to overcome two persistent challenges -- the "wasted senior year" and high postsecondary remediation rates. Seniors identified as not college ready can use their senior year more intentionally, participating in interventions to prepare them for placement into credit-bearing coursework upon postsecondary matriculation. Eleventh-graders demonstrating college readiness can be more accurately and consistently identified and encouraged to more effectively use their senior year by enrolling in advanced coursework, allowing them to earn transferable college credits toward a postsecondary credential or degree.