Elisabeth Barnett of the Community College Research Center proposes a new dimension to the general understanding of how best to prepare high school students for higher education. She suggests considering the accumulation of momentum points--specific to college preparatory "experiences" and markers of educational "attainment" in high school--that together provide graduates with a greater likelihood of college success. Together, these critical points can form a "momentum chain"--that is, a path by which students move with increased forward motion toward college readiness. They may be particularly helpful to low-income and first-generation college students, who are disproportionately underprepared. Barnett proposes that students who have the opportunity and supports to accumulate these momentum points are more likely to avoid remediation, persist in college, and graduate with a credential of value within a reasonable amount of time. This paper is one of a series of five reports intended to encourage K-12 and higher education systems to take joint responsibility for student success in the "shared transition zone" of 12th grade and the first year of college. In this series, and in this paper in particular, ways that local high school and college partners can collaborate to support their attainment are suggested. The first section of this paper describes momentum points and momentum chains in more detail and outlines a student momentum framework based on three research-based components of college readiness. The three sections that follow discuss the research base related to each component and ways that high schools and colleges can work both separately and together to promote smoother cross-institutional transitions. The paper then explores some of the practical considerations of co-creating momentum chains in practice, including aspects of co-design, co-delivery, and co-validation. The paper concludes with conditions that could support the development of a system of shared responsibility for building student momentum from high school into college. A tool for monitoring momentum chain experiences and attainments is appended. [For the executive summary, see ED564837.]