The Bill and Melinda Gates Foundation has invested in the development and dissemination of high-quality instructional and formative assessment tools to support teachers' incorporation of the Common Core State Standards (CCSS) into their classroom instruction. Lessons from the first generation of standards-based reforms suggest that intense attention to high quality instructional tasks (City, Elmore, Fairman, & Teitel, 2010; Hiebert and Carpenter, 1992; Hiebert and Wearne, 1993; Jones et al, 1994) and use of formative assessments embedded in those tasks (Black et al, 2004; Clarke and Shinn, 2004; Fuchs, 2004; Tunstall, 1996) are essential if teachers are to meet the demands of the CCSS. Experts from the Shell Centre have developed a set of Formative Assessment Lessons (Lessons) for secondary mathematics teachers to facilitate CCSS-based student mathematics learning and provide teachers with feedback about student understanding and mastery. The tools are designed to target the "instructional core" by: (1) Raising the level of content; (2) Enhancing teachers' skill and knowledge about instruction, content and formative assessment; (3) Catalyzing student engagement in their learning so that they will achieve at high levels (Elmore, 2010). These tools have been in use for two years (2010-2011 and 2011-2012 schools years). This brief highlights and assesses the status of elements of robust implementation of the MDC tools, which are represented by the small blue circles in the Theory of Action. These six indicators, which fall into two main categories--Teacher Beliefs and Knowledge and Classroom Changes--are instrumental in understanding teachers' disposition towards the tools and their perceptions of how their instruction and student learning have changed as a result of their participation in the MDC initiative. Robust implementation should lead to several intermediate and long-term outcomes, among them Broad and Deep Instructional Change. The authors present their findings for this outcome as well. They provide a brief overview of data sources and then examine: (1) the three indicators of robust implementation related to teacher beliefs and knowledge; (2) the three indicators of robust implementation related to classroom changes; and (3) signs of broad and deep instructional change. Brief 3 closes with recommendations and questions. (Contains 22 figures and 3 footnotes.)