Implementation fidelity strongly affected program results. Within schools, the pedagogical coordinator played a pivotal role as the interface between teachers and the expert coaches. Across both tests and all subjects, student learning impacts were systematically, and substantially, higher in proportion to the performance of the pedagogical coordinator on the final certification exam, which we take as a proxy for the coordinator’s engagement with the program and mastery of its content. In schools where coordinators achieved the basic level of certification, math and Portuguese scores on state and national tests were 0.050.09 SD higher; where coordinators achieved “good or excellent” certification, scores were 0.07-0.12 SD higher, and where coordinators scored in the top category of “excellent”, scores were 0.13-0.23 SD higher. These are significant impacts over the course of a single school year. Given the low program cost of $2.40 per student, the learning results for the one-third of schools with “excellent” implementation are the most cost-effective yet reported in the literature for a rigorously evaluated teacher development program. These impacts raise the possibility of even larger cumulative effects if teachers’ use of new and more effective classroom practices is reinforced and refined over time and professional interaction in these schools becomes a habit. Whether this outcome is more likely than fade-out of the new practices is something that requires further research. But the one-year results strongly suggest that well-implemented programs to raise teachers’ classroom effectiveness through observation feedback and coaching are a promising strategy for “whole school” improvement.

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