The vision for science education set forth in "A Framework for K-12 Science Education" (NRC 2012) makes it clear that for today's students to become the scientifically literate citizens of tomorrow their educational experiences must help them become mathematically proficient. "The focus here is on important practices, such as modeling, developing explanations, and engaging in critique and evaluation" (NRC 2012, p. 3-2). Mathematics is fundamental to modeling and providing evidence-based conclusions. The "Framework" also includes "using mathematics, information and computer technology, and computational thinking" in its list of eight essential practices for K-12 science and mathematics (NRC 2012, p 3-5). This article discusses what it means for students to be mathematically proficient in the context of science and makes connections in math with the Common Core State Standards. (Contains 6 figures and 1 online resource.)