The teachers at Desert Sun Elementary School began implementing a response-to-intervention (RTI) approach to serve their students. In line with RTI principles, they analyzed data and discussed student instructional needs. The teachers quickly realized that the students with the greatest needs were learning not only the many concepts in the general education curriculum, but also a smaller set of different concepts in supplemental instruction. The teachers were concerned with the differences between the general education, or core curriculum, and the supports these students received in supplemental instruction. The teachers decided they needed a way to align instruction for the students who struggled most, to ensure that concepts, skills, and strategies taught in the core curriculum are revisited in supplemental or tiered instruction. Additionally, because they were targeting specific reading skills, they needed to think about how to teach and remediate skills that are fundamental to successful decoding, vocabulary learning, fluency, and comprehension. The teachers heard about some nearby schools implementing a professional development process called Lesson Study. They researched Lesson Study and realized that it had the potential to help them plan collaboratively to create aligned RTI instruction. As a school, they made a decision to implement Lesson Study to see if it could help them develop more aligned RTI instruction.