Educators and researchers have been fighting the reading wars for the last century, with battles see-sawing literacy instruction in American schools from phonics to whole language and, most recently, back to phonics again. Over the last decade, 32 states and the District of Columbia have adopted new "science of reading" laws that require schools to use curricula and instructional techniques that are deemed "evidence-based." Such reading programs include direct instruction in phonics and reading comprehension skills, such as finding the main idea of a paragraph, and efforts to accelerate learning tend to double down on more of the same skill-building practice. The authors conduct the first-ever experimental study of this topic, based on randomized kindergarten-enrollment lotteries in nine Colorado charter schools that use an interdisciplinary knowledge-based curriculum called Core Knowledge.