This study estimated the impacts of the EducAcción-PRI Promising Reading Intervention, a project to support the use of assessment to improve teaching and learning in primary schools in Honduras. The authors examined impacts on Honduras’s national end-of-grade (EOG) test in reading and math for third graders. They randomly assigned 180 primary schools into three groups: a treatment group in which implementer EducAcción provided training and ongoing support to teachers and principals on using EOG assessments to develop school action plans to improve learning; a second treatment group in which EducAcción provided the EOG intervention as well as materials, training, and support to administer formative assessments (FA) and use their results to develop classroom action plans; and a control group that received the usual support from the Ministry of Education. The study was conducted in two urban areas and two predominantly rural departments. Compliance to treatment assignment was high. The EOG component increased third grade reading scores by 0.15 standard deviations, which is equivalent to increasing the percentage of correct answers by 3 percentage points, to moving 8 percent of students to a higher one of the four performance levels reported for EOG scores, or 2 months of instruction. The FA intervention significantly improved reading scores by an additional 0.14 standard deviations. The EOG impacts were almost entirely driven by impacts in urban schools and the FA impacts were almost entirely driven by impacts in rural schools. Impacts on math were similar, but less significant.