As much as "our " school is flexible (and I really think we are blessed), it will not allow partial homeschooling/partial enrollment.
It has to do with funding.
That is why we are persuing individualized education during regular school hours and school sees little or no problem with that.

We are heavily involved, and I guess they feel more secure that I won't come out with some elaborate plan and then leave it for the school to quide my kids through it. They know that my kids will get all the support they need from us DURING SCHOOL HOURS.

Example: Last year while my daughter was in 4th grade, math level in her class was worst than terrible. It was just a cruel joke. I learned about Aleks on this site and suggested it to DD's teacher. Her and P picked out 4 other kids (out of 50), who were also bored to death in that math class, and they bought Aleks for those 5. Decision was made that the kids will be working on Aleks 4 times a week during regular math class. Kids needed supervision, and school could not provie an adult to stay with them . Teacher approached us, the parents of those 5 kids, asking for help. Another mom and I volunteered. But since this other mom was not very reliable and did not keep her promise, I ended up supervising them all four days. Was it easy ? - NO! It was during 4th period, so totally midday and I had to make a special trip to the school each of those days (about 12 min. drive each way). It was insane, to tell you the truth, but it did help my daughter tremendously, she became much, much better in math and it all happened during school hours, which for me was priceless!I did not have to "unschool" her at home any more!
But there was also another benefit to this whole insanity - the school saw me as a very involved parent, and by helping my D I helped 4 other kids. So now when we are bringing the possibility of other online programs to the table , they know that I will be there should help become necessary.
(thank goodness my work schedule allowed for all that insanity)