Information about LLI can be found at:
http://www.heinemann.com/fountasandpinnell/lli_Overview.aspx (Heinemann/Fountas & Pinnell/Houghton Mifflin Harcourt)
Leveled Literacy Intervention (LLI) is designed as a small group daily intervention for students who are having difficulties with phonics, fluency, or vocabulary. The curriculum, outlined in a highly specific manual (often overly specific, according to the instructor), includes specific enjoyable activities (e.g. acting in a play or debate), a significant amount of modeling and direct instruction in phonics rules, group discussions as reinforcement and further learning, and “word work” in a writing journal. According to the National Center on Intensive Intervention (n.d.), this intervention was developed by Fountas & Pinnell and is designed for groups of 3 students in 30 minute sessions, 4-5 times a week for 14-18 weeks.
The What Works Clearinghouse has not published a review of LLI at this time that I was able to find. However, as mentioned previously, the National Center of Intensive Intervention outlined one study on LLI that indicates some moderate student gains (Ransford-Kaldon et al., 2010). The effect sizes they found, based on the Fountas and Pinnell Benchmark Assessment Systems for grades K-2, were .76 (Kindergarten), .81 (1st grade), and .39 (2nd grade), and also found some effects based on DIBELS assessments, ranging from small to large depending on measure. Heinemann, owner of the assessment, further outlines this and another independent study on their website (http://www.heinemann.com/fountasandpinnell/researchLLI.aspx), which indicate significant success in helping students catch up to grade level in both rural and suburban settings (Ransford-Kaldon et al., 2010) and urban settings (Ransford-Kaldon et al., 2013). Overall, this evidence seems to indicate that LLI is successful in enhancing student outcomes of reaching grade level in reading, though more research would be helpful. The somewhat rigid curriculum may be an area of concern for implementers, but these lessons can be supplemented with other materials if students have specific needs.
National Center on Intensive Intervention (n.d.). Leveled Literacy Intervention System. American Institutes for Research. Retrieved from http://www.intensiveintervention.org/chart/instructional-intervention-tools/12860
Ransford-Kaldon, C. R., Flynt, E. S., Ross, C. L., Franceschini, L., Zoblotsky, T., Huang, Y., & Gallagher, B. (2010). Implementation of Effective Intervention: An Empirical Study to Evaluate the Efficacy of Fountas & Pinnell’s Leveled Literacy Intervention System (LLI). Center for Research in Educational Policy (CREP). Retrieved from http://www.heinemann.com/fountasandpinnell/research/CREP1_EXECSUM.pdf.
Ransford-Kaldon, C.R., Ross, C.L., Lee, C.C., Flynt, E.S., Franceschini, L.A., & Zoblotsky, T.A. (2013). Efficacy of the Leveled Literacy Intervention System for K–2 Urban Students: An Empirical Evaluation of LLI in Denver Public Schools. Center for Research in Educational Policy (CREP). Retrieved from http://www.heinemann.com/fountasandpinnell/research/LLIEfficacyStudyReport2012.pdf