Hi - I talked a little bit with the folks who do K12 in MN a while ago. I think the flexibility lies in working at your own pace, and not in choosing curriculum. Specifically, I asked about what happens if your child goes through the curriculum at a faster than normal pace. They said they could just move ahead in the curriculum, but that when it was time for state testing, they would still take the test for the grade they were assigned to. I didn't check more into it, because I was just curious but not really interested at the time. I would recommend calling each of the online educators and ask them all of your questions.
