One activity to keep your teens busy during the summer is of course to send them off to summer school. That's what my oldest daughter is doing, she's going off to summer school.
My middle child Jade, though, will be spending her summer volunteering. She will be working in our main library's archive collection, duplicating and indexing material. She's excited because she will be getting out of the house. I'm excited because she will be learning a new skill and learning how to deal with people in the workplace.