The Leveled Literacy Intervention (LLI) system was developed by Irene Fountas and Gay Su Pinnell to provide small-group literacy intervention for struggling readers in grades K-3. LLI lessons follow a consistent format of phonics, fluency, comprehension, and writing activities using leveled texts matched to students' abilities. Two studies found that LLI significantly improved students' reading achievement over the course of 14-20 weeks of daily small-group instruction. Fountas and Pinnell continue expanding LLI to serve students through middle school.