California's K-12 enrollment is projected to decline for the next two decades, driven by falling birth rates, reduced immigration, and out-of-state migration. With fewer students, districts receive fewer state dollars and may be forced to make tough decisions, including reductions to programs, staff, and/or schools. However, budget realignment does not have to lead to fewer opportunities for students. In fact, whether intentional or not, budget realignment almost always results in changed programs, schools, or systems. District leaders have a choice: proactively shape these changes or reactively respond to declining enrollment. This toolkit aims to support district leaders in proactively responding to declining enrollment. It provides practical tools, resources, and guidance on redesigning school systems in a resource-constrained environment, drawing on research and examples of redesign efforts aligned with the science on how students learn and develop.