Identifying components of teaching that make a difference in children's learning is an ongoing challenge in our field. Focusing on teaching that is responsive to children's fraction thinking, we decomposed responsiveness into the instructional practices of questioning to support and extend children's thinking, noticing children's thinking, and anticipating children's thinking. We worked with 49 teachers in grades 3-5 in multiyear professional development and assessed their expertise in each of the practices. We also assessed their students' fraction achievement at the beginning and end of the school year. Correlational analyses revealed significant moderate relationships among teachers' expertise in the three practices, and a multilevel regression analysis revealed significant positive relationships for both expertise in teacher questioning and years of professional development with children's fraction achievement. [For the complete proceedings, see ED630060.]