My biggest piece of advice is to be sure they're going to do what they say/you think they're going to do. If something isn't written down, you don't have any guarantees. You don't want to have miscommunications, which are no fun for anyone.

Example: What are your DD's approximate skill levels? If she's reading at, say, a 2nd grade level when she starts K, will the school be able to accomodate her? If so, what will they do, specifically?

I think it's important to nail down details before you start at a school.

Oh, my DD4 has a late August birthday and I'm hoping to start her in Grade 1 this fall.

Val