In this study, relationships between entry characteristics, in-class behavior, self-report measures of student cognition, and achievement during motor skill instruction were examined. Fifty-six sixth-grade students participated in a 4-day instructional unit on the forearm pass in volleyball. All classes were videotaped to code in-class behavior. Data collection included skill pretest and posttest, Harter’s Perceived Competence Scale, forms about the errors made during practice, and a Cognitive Processes Questionnaire (CPQ). Correlates of achievement, as reflected by residual gain scores, were perceived competence, student reports of attention, and variables indicating the quality of practice. Relationships between entry characteristics, in-class behavior, and measures of cognition were evaluated using canonical correlational analyses, and these relationships suggest that entry characteristics are important factors in how students interact in achievement settings. The results of this study show that investigating the complex relationships between these sets of variables can yield results that clarify how students effectively mediate instruction.