The study examined the role of motivation in students' performance and engagement in elementary and middle school physical education. Cross-lagged relationships between performance and engagement were investigated across Grades 6-9. A total of 763 (365 girls, 398 boys) Finnish school students (11- to 12-year old) were followed across three years. Students' expectancy beliefs, attainment, intrinsic interest, utility value, and effort were measured using self-report questionnaires, whereas grades were retrieved from the school records. The study showed expectancy beliefs and intrinsic interest values to explain performance, whereas attainment values for girls and intrinsic interest value for boys facilitated the engagement. Although girls and boys were differently motivated, these differences were stable across time. This study supports the utility of the Expectancy-Values Model as a framework to understand motivation. We recommend educators to facilitate students' expectancy beliefs, importance, and intrinsic interest to increase students' performance and engagement in school physical education.