HELP WITH ONLINE SCHOOLING?

Okay so I am 12 and I might have to do online schooling because of my schedule with gymnastics that I might be starting. I have been looking for those online schooling things and I found k12. (I am going into 7th grade by the way.) But I would only have a limited amount of time for school because of my schedule and I don't know if k12 lets you only do school for certain amounts of time. My schedule would be something like an AM gym session, lunch/school, PM gym session, and so on. HELP? Websites??