A broad range of factors go into weighing how well the nation's schools are living up to their responsibility to ensure that students are on track academically and prepared to take their place in a complex, ever-changing society. This third and final installment of "Quality Counts 2018" digs deeply into test scores, high school graduation rates, and other data that focus on the student achievement piece of that picture. In addition, the report analyzes a wealth of socioeconomic and educational data that chart the trajectory toward success in each of the states and for the nation as a whole. Articles in this issue's Quality Counts report include: (1) The Testing Ritual Continues, But Is There Something Missing? (Alyson Klein); (2) What Lies behind Middling Results on K-12 Measure (Alex Harwin); (3) How States Seek to Make Gains among Younger, Older Students (Christina A. Samuels); and (4) What's behind the Myriad Factors That Make up Someone's Chances for Positive Lifetime Outcomes (Sterling C. Lloyd). [For the first installment in this three-part series, see ED580226. For the second installment, see ED586202.]