Faced with the achievement demands of the No Child Left Behind Act and high-stakes testing, principals are being called on to provide leadership that ensures that their students demonstrate mathematical proficiency. To accomplish this goal, it is important for principals to understand what mathematical proficiency is and how they can promote it in their schools. Mathematical proficiency has five key components and instructional programs should address all of these components in a coherent and balanced manner, rather than focusing on one to the exclusion of another. Conceptual understanding is comprehension of mathematical concepts, operations, and relations.