Twenty-one fourth graders are actively listening and constructively critiquing mathematical statements. Each student is eagerly participating in mathematical discussions that involve multiple strategies to discover solutions. What a dramatic change since the first months of school when the same students sat as quiet as stone statues, hoping their teacher would just tell them how to solve the problem. This mathematics classroom has transformed from students blurting out solutions and arguing over correct answers to a group that collaboratively perseveres through problem solving. Student cooperation is evident through the desire not only to justify strategies but also to learn different strategies from peers. With many states adopting the Common Core State Standards for Mathematics (CCSSM) (CCSSI 2010), teachers are seeing a shift in the way they are expected to have their students engage in mathematics instruction. Teachers are charged with pressing students to provide meaningful explanations to help support higher level mathematical thinking and reasoning. The Common Core's Standards for Mathematical Practice (SMP) state that students should engage in discussion that constructs viable arguments and critiques each other's reasoning (SMP 3). During mathematical discussions, students should be able to "justify their conclusions, communicate them to others, and respond to the arguments of others" (CCSSI 2010, pp. 6-7). This article will detail the value of math talk and five strategies for building such a community in the classroom: (1) Discuss why math talk is important; (2) Teach students how to listen and respond; (3) Introduce sentence stems; (4) Contrast explanation versus justification; and (5) Give an example.