Effects of a Structured Explicit Phonics Program with Decodable Books on Early Reading Acquisition in Dominican Public Schools

Explicit phonics instruction and decodable texts are well supported by evidence, yet little is known about how such programs perform when implemented at scale in low-resource, Spanish-speaking public school systems. This study evaluated Aprendiendo a Leer en Primero, a first-grade program combining the Kalulu phonics methodology with decodable books, in 22 public schools in the Dominican Republic, using a mixed methods intervention design. Schools were cluster-randomized, with stratification by district, to an experimental (12 schools) or control condition (10 schools) (N = 830 children assessed at pretest and posttest). Analyses of covariance adjusting for baseline letter knowledge, phonological awareness, and oral comprehension showed that the experimental group outperformed the control group in letter knowledge and in syllable, word, and pseudoword reading accuracy, with small effect sizes, and no differences in phonological awareness or reading comprehension. The advantage was concentrated among children who entered first grade with greater letter knowledge. Implementation monitoring revealed wide variation across schools in instructional time lost to strikes and reduced schedules and in the use of the decodable books, and school results did not map directly onto dosage. A teacher survey (n = 28) and two focus groups documented high acceptability, with close instructional coaching identified as the main perceived success factor, alongside tensions with competing national programs. The findings support continuing the program while adding differentiated support for children with the weakest initial skills, protecting coaching quality, and planning for teacher turnover in future scale-up phases.