This paper illustrates how high-quality preschool has the potential to serve as an intervention within normal populations. Although it is well known that targeted Early Interventions can protect the development of young children from developmental risks, there remains less evidence concerning universal preschool education. To address this disparity, a longitudinal secondary analysis was conducted that examined the psychological development of 2,862 English preschoolers between the ages of 3 to 5 years. A series of aggregated multilevel structural equation models indicated that at age 5 years, instances of significantly protected development were more strongly evidenced when examining (a) cognitive rather than social development, (b) child rather than family-level risks, and (c) the quality of the processes taking place within preschools rather than just the structures. Finally, for preschools that featured only high-quality structures, any partial protection of development was limited to instances of longer durations of child attendance. (Contains 6 tables and 3 figures.)