I taught for many years at the primary school level and really disliked it when parents took their kids out for trips. I can give some work, but you can't recreate what goes on in a classroom.
That being said, as a parent with two young children, I am now all for taking your kid out to save money and beat the crowds (I'm no longer teaching full-time BTW). I really don't think in the long run, a child will be damaged by missing a few days. Remember though, that every child is different and your child's academic capabilities should be taken into consideration. My daughter is no problem, but we will be working with my son during the summer to boost him as he enters 1st grade. The other thing is, you need to choose your time. We are aiming to go Dec 11-17 2010. I know from experience, this close to Chistmas break, nothing new is going to be introduced. There are also no standardized tests at this time. By all means, get that schedule before you go, because that is a problem. I would also probably avoid the month or so before those tests as there is a lot of review going on.
We also do not do this every year. They missed two days in 2008 as we went over Columbus Day weekend. This time it will be a week's trip. I really don't think that it should matter what the school's policy is. Your child will be marked as an "illegal absence." This can go on a permenant record, but it is more for chronic absentees, not Disney visitors.
Lastly, if your child is absent a lot due to illness, then I would do something else. We had a lot of this with my son this year as he was just starting in a new school environment (he's sick today-again!).
Hope this helps!
Jessica