"Transforming Science Assessment: Systems for Innovation," is a series of resources designed to provide state education leaders with: (1) Information about how states are currently pursuing statewide assessment systems in science; (2) Analyses of what features influence different approaches, with an eye to supporting state leaders as they make their own decisions regarding science assessment systems; (3) Detailed state profiles that highlight how and why some states have made decisions regarding designing and enacting different examples of systems of assessment; and (4) A how-to guide for policymakers looking to enact systems of assessment in science. While there are common features of state-led assessment systems, states enacting these systems have made different decisions about how to design and implement their system based on their priorities, values, and state contexts. Discussed here are three different models for state-led assessment systems that are currently being developed and implemented: (1) The Centrally-Signaled Assessment System; (2) The Centrally-Mediated Assessment System; and (3) The Centrally-Planned Assessment System.