This paper outlines 22 principles of practice that serve as criteria by which to judge the developmental appropriateness of an early childhood curriculum. The principles lead to the assertion that young children as learners are greatly supported when a "project approach" is used--e.g., when their early childhood education experience includes opportunities for investigations of phenomena in their environments. Criteria of appropriateness of curricula and pedagogy are discussed, along with explanations of the developmental approach to curricula and teaching practices. The 22 principles of a project or developmental approach include: (1) taking into account those aspects of learning that change with the age and experience of the learner; (2) taking into account two equally important dimensions of development--normative and dynamic; and (3) children's dispositions to be interested, engaged, absorbed, and involved in intellectual effort are strengthened when they have ample opportunity to work on a topic or investigations over a period of time. (BGC)