Background: Failure to learn early reading skills leads to lower reading comprehension later in elementary school (Double et al., 2019; Paige et al., 2019), which can then lead to poverty, underemployment, and increased likelihood of being incarcerated (World Literacy Foundation, 2018). Early reading skills are best developed in kindergarten through third grades by teaching (a) language and vocabulary, (b) the awareness of the segments of sounds and how they link to letters, (c) how to decode words and analyze word parts, and (d) reading connected text every day to support reading accuracy, fluency, and comprehension (Foorman et al., 2016). Although research has clearly demonstrated the positive effects of systematically teaching phonemic awareness and phonics in kindergarten, many commonly used reading curricula do not adequately incorporate those foundational skills (EdWeek Research Center, 2020). Purpose: Given the demonstrated positive effects of systematically teaching phonemic awareness and phonics in kindergarten, the current study was implemented to examine the impact of a supplemental foundational reading program on early reading skills among students in kindergarten. The following research question guided the study: What are the early reading skills of kindergarten students who participated in a year-long supplemental foundational reading program in comparison to students who did not receive the supplemental program? Settings: This study was conducted in 21 elementary schools in one school district in north central Florida. Populations: We focused our study on students performing below the beginning-of-the-year full sample median DIBELS composite score. The full sample median score was 306, which resulted in a final sample of 1,084 kindergarten students. Intervention: Students in the treatment condition received the UFLI Foundations program (Lane & Contesse, 2022). UFLI Foundations follows a scope and sequence designed to ensure that students systematically acquire each skill needed and learn to apply each skill with automaticity and confidence. The scope and sequence begins with the introduction of phonemes (speech sounds), graphemes (the letters and letter combinations used to represent speech sounds in writing), and the correspondences between them. Students learn to apply this knowledge of grapheme-phoneme correspondences to read and spell words. As students progress through the scope and sequence, they learn about more complex concepts, such as syllables and morphemes, which equips them to read longer words. Research Design: We used a quasi-experimental design (QED) and established baseline equivalence for students in the treatment and control conditions using propensity score matching. The comparison group, which received business-as-usual (BAU) instruction, was created using students in the same grade-level during the prior year. Data Collection and Analysis: Early literacy skills were measured using the DIBELS¨ 8th Edition Assessment Composite Score (University of Oregon, 2023). The DIBELS assessment was administered each year at the beginning of the school year in September (pretest) and again at the end of the school year in March/April (posttest). The school district provided the authors with the DIBELS data for all K-1 students in the district for two consecutive years at the end of the 2021-2022 school. Files had a unique anonymous identifier for each child and a series of demographic characteristics, including grade, gender, race/ethnicity, and special education status. We used the pretest scores and demographic variables, which included race/ethnicity, gender, free and reducedprice lunch status, and special education status, to propensity score match students in the UFLI condition to students in the control condition. This approach ensured baseline equivalence on all covariates and pre-test measures. We estimated propensity scores using logistic regression. Specifically, treatment was be coded as a dichotomous indicator and used as the dependent variable in a logistic regression model, with all demographics and pretest measures. Next, we used each student's estimated propensity score to match students in the treatment condition using the one-to-one optimal matching method to a student in the control condition by finding the smallest average absolute distance across all the matched students. We used the one-to-one optimal matching algorithm with matchit (Ho et al., 2017) and optmatch (Hansen et al., 2016) packages in R (R Core Team, 2021). To confirm equivalence, we calculated standardized mean difference effect sizes (g) for pre-test scores, by treatment condition, where equivalence was defined as g < 0.25 standard deviation units (WWC, 2021). Finally, we assessed impacts of UFLI Foundations on student outcomes using a series of multilevel models. Results: First, we examined the pre and post test scores by treatment condition for the baseline equivalence propensity score matched students. Table 1 presents the descriptive statistics. Based on pre-test scores, the students were equivalent at baseline on the DIBELS Composite score, with g < 0.05 standard deviations. Based on posttest scores, the students receiving UFLI Foundations performed much higher at posttest than students in the control condition. The effect size, controlling for pretest only and using the pretest standard deviation, was g = 1.20. Next, we estimated the multilevel models (see Table 2). The treatment coefficient was statistically significant. When accounting for student characteristics, the covariate adjusted effect size increased to g = 1.44 for students in kindergarten. With regards to covariates, we found that Black students scored lower than White students, while Asian students scored higher. Student with disabilities also performed significantly lower than their typical peers. Finally, also examined teachers' implementation fidelity via ratings by literacy coaches. Each teacher was rated from 0 to 4 on both adherence and dosage, with 4 indicating high fidelity using a standard observation rubric. Analyses indicated that implementation fidelity predicted student reading growth (Figure 1). That is, teachers who implemented UFLI Foundations as intended produced greater reading growth in their students. Conclusions: Data from this district-wide pilot study provide evidence that UFLI Foundations is effective for improving foundational literacy skills. Students who received instruction using UFLI Foundations in the 2021-22 school year significantly outperformed students who did not receive UFLI Foundations instruction in 2020-21. Teachers with high implementation fidelity produced substantially greater student growth, compared with teachers with lower levels of fidelity.