The purpose of this session is to articulate a research framework that centers teachers’ voices when trying to understand how teachers use curriculum materials in the classroom. Operating in the context of highly structured lesson plans, the approach identifies ways in which teachers exercise their professional discretion to modify the lesson and frames conversations to elaborate the motivations driving the teachers’ choices. The approach has been iteratively refined across three studies; taken together, the studies provide evidence for the value of listening to teachers and being responsive to their voices during implementation. The research framework uses the lens of modifications, or changes to the intended lesson plan implemented within one class period. Modifications can be large or small, additive or subtractive. For example, in a lesson with a section for independent student practice, a large modification might be skipping the practice section entirely. Or, during a lesson focused on blending of initial sounds using 3 example words, a small modification might be extending the exercise by adding extra words. Researchers observe the lesson, noting any modifications; after the lesson, the researchers select some of the modifications and ask the teachers why they made the choices they did. Analyses of teachers’ explanations highlight the importance of understanding why teachers make the choices they do. For example, a teacher who skipped the independent practice section because they don’t think their students are ready to do the skill on their own suggests that the teacher is exercising agency and using her knowledge of her students to inform her decision-making. Insights such as this one can guide decisions on projects. It may be that while the intention of the teacher was guided by knowledge of students, the end result is not desirable from the project’s point of view. Understanding why the teacher made this choice provides implementers with better and targeted ways to address choices that impact the overall goals of the project. In this presentation, we draw on data from an exploratory case study to understand use of new mathematics materials in Liberia, a more in-depth case conducted in Malawi on teacher use of reading materials, and finally, a systematic study examining how reading teachers use materials across four Sub-Saharan African countries. We use each case to highlight both an aspect of the research framework and instances of modifications to project implementation driven by teachers’ voices. By focusing on teacher voices, we disrupt the deficit notion that teachers are “resistant” to change, or do not “understand” new pedagogies. Instead, we aim to value teacher voices and integrate their insight into implementation programs. By doing this, we not only raise the likelihood of successful use of new materials and pedagogies, but we also develop more responsive pedagogy that better matches existing classroom cultures.