[NOTE: full document is in Spanish and the complete volume of the publication can be found here] This study’s aim is to examine the effect of informal environmental education, through participation in the Programa de Escuelas Sustentables – PES (Sustainable School Program) of the non-profit organization COSUAM of Puerto Rico, in the academic achievement of high schools students. The analysis was conducted through the development of a scale that allowed the classification of the schools according to their participation in the program. It is expected that schools categorized as “very active” will obtain a higher academic achievement score in the Pruebas Puertorriqueñas de Aprovechamiento Académico (PPAA) standardized tests of the academic year 2014-2015 than the schools that were not so active. Pre-existing data were used for this study, including the results of the standardized tests (PPAA) and general information about the schools, which are public records available to through the Department of Education’s website, and the information facilitated by the PES program’s director. The results of this study show that there is a moderately significant tendency for the increase of academic achievement of science with the level of participation of the schools in the program. Results also demonstrate that there is a significant negative relation between percentage of science classes attended by highly qualified teachers, graduation rate, and increase in academic achievement in science. This preliminary study had two principal contributions: establishing a relationship between academic achievement and this informal environmental education program and establishing a rubric to categorize schools and give them a gradation as a function of their participation in the program. It is emphasized that more studies of this kind are necessary, with more schools (public, private, and different grades) and with other environmental education programs, to further examine this topic.