The goal of this study is to improve our understanding of the variation in quality within and across classrooms. To achieve this goals we use two sources of rich data on program quality and child outcomes from centers serving preschool-age children. The study has three aims: (1) determine how to combine measures of the characteristics of individual staff members in a classroom to best capture quality at the classroom level; (2) determine whether quality should be measured at the level of the staff member, classroom or center; and (3) determine whether there are ways to improve the efficiency of measuring quality at the center, classroom, and staff-member levels. The research questions include: (1) How should staff quality attributes be combined to create classroom level scores that reflect actual quality?; (2) What is the optimal unit of analysis in studying ECE quality?; and (3) Are there ways to increase efficiencies in assessing ECE center quality?