Early literacy intervention is critical to students who are struggling to progress in reading. One intervention aimed at supporting students in the first-grade is Reading Recovery (RR). The purpose of this study was to explore the sustainability of gains achieved by first-grade students, on the STAR reading assessment, who exited the Reading Recovery intervention during the 2014/2015 school year. The growth and sustainability of growth were examined across five years: 2014/2015 to 2018/2019. The study took place at a large mid-west school district using data from students who were in the school district all five years. The data collection procedure was ex post facto, using data that had previously been recorded in the databases. There were four main research questions and one sub-question. Gains during the school year 2014/2015 were examined on the Observation Survey assessment using a paired samples t-test. Students who successfully exited the RR program had a mean entry text level of 5.08 and a mean exit text level of 16.81 with a mean increase in text levels of 11.731. The significance value was p < 0.001. Additionally, an independent samples t-test examined the differences between recommended action (RA) students and discontinued (D) students. The recommended action (RA) student mean entry text level was 0.73 and exit text level was 7.38. There were statistically significant differences in Observation Survey text levels between discontinued (D) students and recommended action (RA) students. A one-way repeated measure ANOVA and tests of significance for the one-sample t-tests were done to analyze the data in comparison to the STAR reading 25th percentile cut score. Year 2014/2015 provided 19.10 points above the 25th percentile score. Years 2015/2016 to 2018/2019 show average differences below the 25th percentile cut score. These differences were below the 25th percentile, but varied in average difference/distance away from the cut score. Year 2016/2017 was very close to the cut score (-1.25), while 2018/1019 was -32.77 points away from the 25th percentile score. A repeated measure factorial ANOVA revealed differences on the STAR assessment scaled scores in grades one through five based on exiting (D) and not exiting (RA) the RR program. The mean z scores over all 5 years combined were always higher for the discontinued (D) students. The interaction was not statistically significant. The growth lines for the two groups remained nearly parallel throughout the five-year period. There was a statistically significant difference on the STAR reading scaled scores in grades one - five based on successfully completing the Reading Recovery program (D) and not successfully completing the Reading Recovery program (RA). Lastly, there was a statistically significant difference (p <0.001) in the percentage of students who qualified for special education services between those who did not exit the RR intervention (RA) and those who did exit the RR intervention (D). Educators may find this research useful when exploring early literacy interventions. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]