Research Findings: Kindergarten is the gateway to education and a point of great variability in children's knowledge and skills. As a result, there is keen interest in kindergarten entry assessments (KEAs) to understand and address gaps in early skills. This study rigorously investigated the Commonwealth of Pennsylvania's Kindergarten Entry Inventory (PA KEI). Multilevel factor analyses provided evidence for three factors--"Emerging Academic Competencies," "Learning Engagement Competencies," and "Communication Competencies." Measurement invariance analyses indicated that these factors were invariant across gender, race/ethnicity, dual language learners, and special needs status. Support for concurrent convergent and divergent relations was found only for scores on the "Emerging Academic" and "Learning Engagement Competencies" factors. Analyses of classroom-level variance in PA KEI scores indicated that teacher education and experience predicted between-classroom differences suggesting that teacher characteristics may influence ratings of children's skills. Practice or Policy: This study provides evidence to support the use of scores on two factors of the PA KEI with all children to identify skill gaps and guide instruction to close them. Findings from this study can also be used to inform professional development on the PA KEI. Finally, this study provides a model for other investigations and efforts to improve teacher-report KEAs.