The ExceleRate Illinois tiered quality rating and improvement system was examined in a validation study conducted by the Frank Porter Graham Child Development Institute (FPG) in collaboration with American Institutes for Research (AIR). ExceleRate Illinois provides systems for monitoring and improving child care quality and providing clear information to families about the quality of the early care and education (ECE) of enrolled centers and schools. This study sought to examine the validity and reliability of the ExceleRate Circles of Quality. The validation study answered the following questions: - To what extent does ExceleRate Illinois differentiate levels of quality in programs overall and across each domain? - To what extent does a program's score on each domain contribute independently to its overall rating? - What combination and/or weighting of indicators best discriminate levels of quality? - Do children who participate in programs rated at higher Circles of Quality overall and across particular domains demonstrate greater gains in child outcomes compared to children who participate in programs rated at lower levels overall and across domains? (author abstract)