<p>Early childhood teachers and mathematics teacher educators use student-centered mathematics routines like Notice and Wonder and Clothesline Math to promote sensemaking, encourage curiosity, and make mathematics more accessible for students. We used qualitative content analysis to examine 67 digital artifacts of practicing teachers’ implementations of routines they were learning in a mathematics and technology education course. Using the four principles of productive disciplinary engagement (problematizing, authority, accountability, and resources) as an analytic framework, we coded teachers’ photos and written reflections to better understand how enactments of their routines created opportunities for mathematics learning. Forty-nine of the 67 artifacts showed evidence of problematizing, typically featuring explanatory text alongside visuals that connected student mathematical ideas back to posed mathematical challenges. We also created two additional codes (depth of problematizing and depth of accountability) to further describe how the artifacts tied the routine to learning goals and highlighted students’ verbal contributions. Findings suggest that although teachers valued student-centered instruction and mathematics conversations, they may need additional support in connecting classroom activities to curricular learning goals and promoting equitable participation. This research offers implications for mathematics teacher educators seeking to deepen early childhood teachers' understanding of effective student-centered mathematics instruction. The principles of productive disciplinary engagement can scaffold teacher reflection and strengthen opportunities for mathematical reasoning during routines.</p>