Observational studies comparing child outcomes in early care and education classrooms of differing quality are often confounded by between-child differences. A within-child design, tracking children across contexts, can identify the effects of quality with less confounding. An analysis of Australian children (N = 1128, mean age 5 years, 48% female, 2.9% Indigenous, ethnicity data unavailable) tracked across pre-K, K, and year 1 (2010-2012) was conducted to assess how changes in observed quality (Classroom Assessment Scoring System) were associated with changes in cognitive development (Woodcock-Johnson III). Thresholds of quality were also investigated. Increases in Emotional Support were associated with improved language development ([beta] = 0.54, 95% CI [0.1-0.99], approximating 2.6 weeks development). Results highlight that emotional quality is an integral and potent component of early learning.