Selected research on the learning and performance of physical skills from a knowledge-based perspective provides the introduction for a discussion of the importance of practice in the developmental skill learning process. Recent evidence on the activity deficit hypothesis as well as knowledge-base differences as they relate to children with movement difficulties in physical activity settings provides the basis from which to present the developmental skill-learning gap hypothesis, which contends that as children with movement difficulties grow older, the skill-learning gap between them and their more physically proficient peers widens across instructional, practice, and competitive settings. Implications and suggestions for the learning and instruction of children with movement difficulties conclude the paper.