In Winter 2017, the Johns Hopkins Institute for Education Policy and Johns Hopkins Center for Research and Reform in Education conducted a research review on the effects of curricular choices in K–12 education for the Knowledge Matters Campaign, a project of StandardsWork, Inc. That review,1 available upon request at standardswork.org, surfaced several important findings, including the following: » Curriculum is a critical factor in student academic success. » Comprehensive, content-rich curriculum is a common feature of academically high-performing countries. » The cumulative impact of high-quality curriculum can be significant and matters most to achievement in the upper grades where typical year-on-year learning gains are far lower than in previous grades. » Because the preponderance of instructional materials is self-selected by individual teachers, most students are taught through idiosyncratic curricula that are not defined by school districts or states. » Research comparing one curriculum to another is very rare and, therefore, not usually actionable. The overarching conclusions from the Johns Hopkins’ review are that curriculum is deeply important, that a teacher’s or district’s choice of curriculum can substantially impact student learning, and that—as a result—the paucity of evidence upon which sound instructional, purchasing, and policy decisions can be made is a matter of deep concern and urgent need.