It ocurred to me as i read this thread, that one of the quesions to ask yourself is "what does our family believe school is for?"
This may help as you are considering your options and I think the each of us would give a different answer.

Of course, none of us wants our chilren to be harmed in school; we want them to be relatively happy, and we want them to learn things.

But, beyond that, what do you think is the purpose of school? Is the goal to have your child learn lots of academic skills and be challenged? Do you want them to have school be a place where they make connections and develop skills which will help them be competitive in HS, College and beyond? Do you want them to participate in a microcosm of the larger community, learning about families that are different than they are? Do you want them to be well coached in sports or other activities? Do you want them to be with people who are mostly demographically like them? Do you want them to be exposed to things that you might never think to expose them to at home (I remember being amazed at how much pride DS took in learniing the Pledge of Allegiance--not something I would have thought to teach him)? Do you want them to get a lot of independence early or do you feel they need more protection at first? Do you think that learning to cope with boredom is an important skill or a frustrating waste of time?

I don't suggest that there are right answers to these questions, but that thinking about what is important to your family is key to making a decision you are comfortable with and able to support even when there is a bad day or two (which there are bound to be no matter which decision you make.)