Even before the release of the National Council of Teachers of Mathematics (NCTM)'s Principles to Actions (2014), teachers paid significant attention to mathematics tasks based on their positive influence on student learning (Doyle, 1988; Kazemi, 1998; NCTM, 1989, 2000). Over the last almost quarter century, we have learned a lot about high-level task design and implementation (Henningsen & Stein, 1997; Stein & Smith, 1998) and instructional moves that support task implementation (Boston & Smith, 2011; Smith & Stein, 2011; Stein et al., 2008). From this research, NCTM articulated a set of high-leverage mathematics teaching practices (MTPs) that were shown to make a difference for students' mathematical understanding and achievement. The lesson study cycle described here leverages two practices that remain somewhat elusive as teachers use their district-adopted instructional materials: (1) implementing tasks that promote reasoning and problem solving, and (2) facilitating meaningful mathematical discourse. The mathematics coach at Washington Elementary School, Kiana (pseudonyms used throughout), worked with one teacher leader from each grade level (K-5) to develop skills related to planning and implementing cognitively demanding tasks and promoting high-level talk.