Formative assessment can raise standards of achievement. In physical education, when formative assessment was incorporated into instruction, students performed better in terms of skills and were more on-task. The purpose of this study was to examine the effects of formative assessment on success and response rate of a sixth grade badminton unit. Specifically, this study aims to study how formative assessments impact response and success rates of the more skilled, average skilled and lower skilled students in a badminton unit in physical education. Sixteen students from two sixth grade classes took part in this study. One class served as the treatment group, where the teacher incorporated formative assessments in her teaching, while the other class served as the control group. The current study found that students in the treatment group were more on-task than the students in the control group based on the response rate. Students in the treatment group had higher response rate, and this difference was statistically significant. Although the treatment group showed a 10% higher mean success rate, the results were statistically insignificant. This study confirmed students were more on-task and had a higher response rate when formative assessments were incorporated into the lesson.