I like jogging to school - it's good exercise, and it makes me wake up in the morning.
I have to run with my (moderately heavy) school bag on, and my bag makes the back of my shirt ride up as I run. (When I take a step, my shirt and bag both bounce, and the bag catches my shirt before it can fall back down.) This makes me pull my shirt down about once a minute. It's very inconvenient.
How can I keep my shirt down so that I can happily run?