The purpose was to examine the effect of an intermittent teaching unit based on the use of an activity wristband combined with other behavior modification techniques on secondary students' weekly objectively-measured physical activity (PA). 176 secondary students (12-16 years) were cluster-randomly assigned into the activity wristband (AWG) and control groups. The AWG performed an eight-week intermittent teaching unit (last 15 min of each session) twice a week. The teaching unit consisted in the following strategies: activity wristband (24 h), adaptative step goals, and educational counseling, among others. Results showed that the AWG students improved activity wristband-measured weekly steps from baseline to the last week of the intervention (p < 0.001). Furthermore, the percentage of AWG students that did at least an average of 10,000 steps per day increased (p = 0.026). The studied intermittent teaching unit increased students' weekly PA, and the proportion of students that achieved the PA.