Nonprofit organizations amplify impact through relationships with K-12 schools, and these schools benefit from provided resources and services. Nonprofit provision of resources and services via schools is theoretically mutually beneficial, efficient, and effective. In practice, however, schools struggle to make the necessary investments to maintain relationships. Why? Through an inductive multimethods study of 81 nonprofit organizations and nine schools that partner with them, we find that schools struggle because it is difficult to effectively manage the temporal costs of the relationships. Principals, teachers, and staff have many demands on their time, and spending additional time coordinating and administrating nonprofit relationships is a challenge. Intersecting survey, interview, and archival data from schools and nonprofit organizations, we find the nine schools take on this operational challenge of managing temporal costs with one of two time logics, defined as a sociocultural belief about time resources at the school. The three charter schools in our study have a fixed logic that views time as a static resource, while the public and Catholic schools have an adaptable logic that views time as a flexible resource. We observe that these logics correspond to the school’s workforce operations, specifically whether or not they rely on external affiliates, such as district/community leaders or parents, to dedicate time to help manage school–nonprofit relationships. Schools with an adaptable-time logic have more time flexibility for managing nonprofit relationships when they rely on this external “workforce” compared to schools with a fixed-time logic that do not. The evidence suggests more generally how organizational culture and time logics relate to workforce operations. We conclude with preliminary evidence of long-term relationship outcomes from a follow-up survey of the same schools in our original study and discuss the implications for improving nonprofit provision of resources and services via schools.