College completion rates in the U.S. are stubbornly low despite the large and rising returns to a college degree. Efforts to increase student success in college have largely ignored a potentially key factor: the instruction that students receive in the sequence of courses that add up to a college education. Improving the quality of instruction may represent a promising path to increasing the number of students who earn high-quality degrees by decreasing frustration and failure, and improving the skills of college graduates. But it is nearly impossible to improve instructional quality without being able to measure it. This report describes a sophisticated set of common final exams implemented in two developmental algebra courses at Glendale Community College in California. These common finals enable instructors and administrators to compare student performance across different sections, and have earned broad faculty support by being implemented in a way that strikes a balance between standardization and the preservation of faculty autonomy. The author shows how data from common finals can be used to measure how much students learn in sections of the same course taught by different instructors, and how instructor characteristics such as education and full-time status are related to student mastery of algebra. The author concludes with four policy recommendations aimed at moving forward efforts to assess and improve the quality of postsecondary instruction and ultimately increase the number of students who earn high-quality credentials. (Contains 17 endnotes.)