Building on the concept of Freirean culture circles, this study reports on the development of supplementary materials to incorporate critical literacy into high school EFL textbooks. Collaborating with two experienced high school EFL teachers in South Korea, critical supplementary materials were developed to compensate for the speaking sections of Korean high school EFL textbooks. Teacher interviews, classroom interactions, and students' surveys revealed five key elements of critical materials that were necessary for students' critical engagement, namely: framing, safer topics, critical questions, critical vocabulary, and writing before speaking. This study shows that critical materials enable teachers' critical literacy teaching practices, helping teachers deal with the dilemma between what is feasible and the principles of critical literacy. With classroom-based examples and discussions, this article offers insights to ELT teachers, materials developers, and teacher educators who strive to promote critical literacy in skill-based ELT classrooms.