Declining youth physical activity levels and lack of aerobic fitness have been well documented with a corresponding rise in obesity levels and health issues. Based on Bandura's social cognitive theory, healthy physical activity levels and aerobic fitness are strongly connected to positive physical activity self-efficacy beliefs. This study examined whether student physical activity self-efficacy, motivation, and effort were different for the FitnessGram-® (FG) 1-Mile Run when compared to the 15-minute Aerobic Assessment Based on Improvement (AABI). A concurrent mixed method quasi-experimental approach measured 5th grade students' physical activity self-efficacy beliefs through a pretest and posttest survey while aerobic assessment scores provided data that measured and compared student performance. Percent improvement and t-test analytic procedures found significant differences between groups and genders. The FG group (n = 131) improved 1.49% while the AABI group (n = 209) improved 22.53%; furthermore, FG girls' percent improvement decreased to -7.56% and the AABI girls' percent improvement was above the average score at 24.21%. Qualitative data collected and coded from teachers' (n = 6) found no noticeable differences in student behaviors or preparation between the FG or AABI groups. A 3-day workshop was created to initiate change in aerobic fitness assessment. Assessing student aerobic fitness based on improvement theoretically builds physical activity self-efficacy beliefs, especially for girls. Positive physical activity self-efficacy beliefs motivate greater student participation and engagement in physical education, which improves aerobic fitness. Social implications from these results indicate that students would increase their physical activity self-efficacy by assessing aerobic fitness based on individual improvement.