The time has come to improve the quality of core courses so that all students have equal opportunities to become prepared for postsecondary education and for work. The purposes of this report are to examine the gap between secondary and postsecondary education in the U.S. and to focus on successful strategies for eliminating this gap so that all high school graduates learn the essential skills they need to be successful in college and work. This report suggests that some students progress toward college readiness in high school, but many lose momentum during their last two years there. ACT research shows that high school courses can be made rigorous and that rigorous content can be effectively taught and learned. The report recommends five action steps that states and schools can take to improve the rigor of high school core courses. (Contains 20 figures and 6 tables.)