Walk round the track. Step up and down a step. Or run up and down a series of steps.
But why does it need to be during the day? If you are still at school you are working the shortest hours you ever will. Why not go for a walk/jog after school, while you are winding down from the school day. As an added bonus it will refresh your mind and body and make study in the evening easier.
Wagon? What do you mean wagon? This is life, not a wagon. You can't fall off life. Get out there and LIVE!