Large achievement gaps have been found in ACT scores between high schools throughout the same state and in comparisons between states. In Missouri, four public high schools have consistently scored four points higher than the Missouri average for years 2007-2011. States, such as Nebraska, Minnesota, and Iowa, have shown consistent above average scores as compared to states with similar participation numbers throughout the nation. Schmoker (2006) believed that due to the existing culture of schools and school leadership, learning from others' successes is often discouraged; therefore, this study was conducted in an attempt to discover the best practices used in high-achieving high schools and states that obtain high student achievement on the ACT. Educational leaders within the top 5% of high schools in Missouri, based on a five-year (2007-2011) average of ACT scores, were surveyed to determine successful teaching strategies and programs educators in these schools are implementing. Leaders from consistently successful states (having higher than average ACT scores with a high percentage of participation) took part in a survey to extrapolate further characteristics regarding high achievement. Furthermore, the trends and the approaches that contribute to student success in states that require the ACT were examined through interview responses. While the study did not reveal any new best practices, the findings supported many best practices already in existence, and most importantly, showed the necessity for the development of a learning culture that emphasizes success and achievement. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]