I myself went to a high school which functioned this way. We started the week in our groups for a 30 min meeting where we set the goals for the week. After that we studied what we wanted. There were workshops all day with english, math etc that you could go to if you had any questions. But mainly you sat with your friends in small groups and studied.

And yes, you were alone responsible for when you took breaks etc. This way of studying were in my opinion much more effective. Sure I perhaps didn't put in as much time studying as people who went to traditional schools did. But once i studied I were much more focused and to be honest. When you sit in a class and the teacher ramps on about something that is of no interest to you, how much are you able to recollect?

Also another positive side of it were that if I had it easy for some topics I could focus others which I had a hard time for. I remember that I didn't study either swedish or math at all in 6th and 7th grade.