Here is a copy of my post that I did on another thread with this topic:
I say take her out of school for the trip, no matter what her school thinks about taking kids out of school for trips. It is not the school's place to decide if your child can miss school for a trip. It is the parent's choice, whereas the school's job is to educate your child. WDW also has many educational aspects. It's not like your kid is sitting watching mindless cartoons for a week or something. A trip is much different than parents who are negligent and just do not take their kids, or make their kids go to school.
Ask her teacher if he or she can put together some schoolwork that she would be doing in the classroom and ask if there is anything that she should plan for, so she doesn't feel behind when she gets back to school. My son is in kindergarten also, and his school is fine with us taking him out of school. We have taken him out for 5 days for the Sept WDW trip and 4 days for a trip to CA for my brother's wedding. We will be taking him out again for 8 days at the end of Feb/early March for the 4/3 deal plus a day at Universal. We are also driving, which will add 2 days (one stop each direction).
People are so concerned about their kids missing school, but seriously...it is not a big deal. Schoolwork can be done outside of a classroom, many schools even offer a homeschool option where you get your work once a week and turn it in to the teacher at the end of each week. I wouldn't worry about it. Enjoy your trip!