Many studies have shown that higher-quality early care and education (ECE) predicts positive developmental gains for the children who experience it. However, much ECE in the United States is not of sufficiently high quality to produce these benefits. Quality rating and improvement systems (QRISs) attempt to improve practice and care quality in ECE settings; both are expected to improve child functioning. However, these systems rarely assess children to determine their effects because of the high costs and assessment burdens involved. Yet including child assessments in the design, implementation, and evaluation of QRISs or other quality improvement (QI) efforts could improve practice and raise care quality. The authors identify five strategies for states to consider for incorporating child assessments into QRISs or other QI approaches. Two of the strategies use assessments to inform classroom practice and to support program improvements. The remaining three use assessments to measure the effects of participating in a given classroom, program, or ECE system on child functioning. The authors' analysis of these strategies relies on research about measuring child functioning and methods for determining the contribution of ECE to developmental trajectories. It relies as well on new research concerning how states have included child assessments in their QRISs. Guidance is offered about when and how to incorporate the five approaches into a QRIS; the value of these approaches depends on the questions to be answered, the stage of the QRIS, and the availability of the resources needed to implement assessments and mount a rigorous research design. A bibliography is included. Individual chapters contain footnotes. (Contains 1 figure and 7 tables.)