Many students in U.S. schools have trouble understanding fractions and Algebra II, the one difficultly occurring at the end of elementary school, the other in high school. One reason is that schools generally focus on one aspect of mathematics--calculation--and often fail to address the second aspect--interpretation. Also responsible is the trajectory of school mathematics, which moves from the concrete and functional in lower grades, to the abstract and apparently nonfunctional in high school. To improve instruction in math, teachers need to focus on communication, connections, and context. Students need to be able to explain in writing the meaning of data, tables, graphs, and formulas; they need to see other content-area teachers regularly using quantitative or logical arguments to tie evidence to conclusions; and they need a good diet of sophisticated, realistic, and meaningful problems to solve.