Background: Childhood obesity increases health risk, and modest physical activity can impact that risk. Schools have an opportunity to help children become more active. Purpose: This study implemented a program offering extra school-day activity opportunities in a rural school district where 37% of students were obese or overweight in 2005 and evaluated program impact over 10 years. Methods: A longitudinal, one-group repeated measures analysis was completed. Participants were all district elementary students from 2006 through 2015 (average yearly enrollment: 3027). Schools implemented new opportunities for children to engage in structured aerobic activity at school outside of physical education class. A KidMinutes measure combined duration, frequency, and participation to describe activity outcomes during one study month annually. Results: Total KidMinutes increased 293% over 10 years. Average monthly KidMinutes per student per school increased 22.4 minutes per year (P < 0.001). Discussion: A school district successfully increased children's physical activity by focusing on adding aerobic activity opportunities to the school day. KidMinutes is an easy-to-use measure for evaluating school activity programs. Translation to Health Education Practice: Using the described methods and measure, Health Education specialists can plan, implement, and evaluate health promotion efforts to increase physical activity among schoolchildren.