Check on gross and fine motor skills. I don't know what you do if the motor skills are not strong enough, but I have discovered that they are really important to early school success. Maybe if the child is really young it is obvious and they get a pass, but in my experience with my child, it doesn't matter how well you read in kindergarten, what you have the ability to understand or what your math skills are. You need to be able to sit in a circle for long periods of time, draw, color, and be ready to write. Period. They don't teach that stuff, they expect it. Reading, writing, and arithmetic, they teach. If children come in already knowing the academic stuff, they don't learn much academically anyway.
So on that note, also ask how they provide instruction to early readers. That will tell you a lot. One of the big problems with single subject acceleration for young children is that they have to figure out how to get themselves to the other class....be aware of time, know when to leave the classroom, navigate the hallways, be assertive enough to walk into the other classroom. That's all hard for little kids and sometimes it doesn't work out, so if they accelerate, ask how those logistics happen.
