I have a friend who has done this with her kids and it has worked well. Mostly the school and teachers worked with her after she worked long and hard to establish good relations.
She pulls them out for specific subjects in which they need more challenging work.
I think the cooperation of the teacher is vital because special, fun things can be planned for when the child is in the room or NOT in the room, as the teacher likes. It can become punitive if the teacher is opposed to the arrangement. That's hard.
There is also the risk of the child becoming "neither fish nor fowl" and feeling out of place both in school and with homeschool groups. I suspect being mostly one or the other is best. (My friend's kids were pulled out for just an hour or so, I believe. That way they didn't miss much and they felt like schoolkids, not homeschoolers.) I think half-days might be too much. (But that's just IMHO...)
I think partial homeschooling or "dual enrollment" is a good option for some families. It just requires a lot of cooperation and communication.
