In recent years educators and policymakers have set a goal that students graduate from high school ready for college and careers. However, as a nation we are far from achieving this goal, particularly for low-income and minority students. For example, in states where all eleventh-graders take the ACT[R], only 27 percent of low-income students in 2010 met the ACT College Readiness Benchmark in reading, with 16 percent meeting the Benchmark in mathematics, and 11 percent meeting the Benchmark in science. Efforts to improve students' academic preparation have often been directed at the high-school level, although for many students, gaps in academic preparation begin much earlier. Large numbers of disadvantaged students enter kindergarten behind in early reading and mathematics skills, oral language development, vocabulary, and general knowledge. These gaps are likely to widen over time because of the "Matthew effects," whereby those who start out behind are at a relative disadvantage in acquiring new knowledge. This report uses information on the percentage of students reaching college and career readiness targets over a four-year period as an indicator of the difficulty of doing so. The report focuses on students who start out far off track--well below the achievement level that those with average growth trajectories need to reach college and career readiness targets in a specified later grade. This report focuses on closing academic preparation gaps over two four-year periods: (1) Grades 8-12: How many students who are far off track in eighth grade reach college readiness benchmarks by twelfth grade?; and (2) Grades 4-8: How many who are far off track in fourth grade catch up by eighth grade? (Contains 11 figures and 9 footnotes.)