If you're interested in educational experiences at WDW beyond simple make-up work, here are a few suggestions. I'm a Social Studies teacher - here in NY 9th grade Social Studies focuses on World History, for which Epcot is ideal. I'd be impressed if a student returned with accounts of interviews with the cast members at each pavilion; in fact, I'd be psyched to help them make up a list of questions to ask about their countries, so that might be a good thing to suggest to her teacher. If that doesn't fit WA curriculum, perhaps a "research" project on the history of Disney - the man, the parks, the corporation - whatever may fit your state standards. My 7th graders write a critical review of "Pocahontas" that analyzes how accurately the film depicts her life and culture, including the relations between the Powhatans and the settlers at Jamestown - this requires research about the settlement and the tribe before watching the movie, as well as a written review. There are other Disney movies that might work, too - and could satisfy an English requirement. Since you are coming from the opposite coast, a report on Florida (history, geography, native flora and fauna, local Native American groups, etc) could be very interesting to folks back home. Oh, and a biography of Ernest Hemingway (or other FL author) or book report on one of his works might appeal to DD's English teacher.
As far as the note to her teachers, I'd explain that while you fully understand the value of your child's education, circumstances force you to take your vacation during school time. Schools love the concept of personal responsibility, so stress that this will be a chance for your daughter to practice that skill. Tell them that you'd greatly appreciate obtaining materials ahead of time and/or opportunities for her to use her time at WDW for enrichment activities like the ones suggested above. If your daughter has a history of responsibility and good grades, say so. If possible, follow up with a phone call to confirm information or discuss details - I know parents are truly supportive if they do make the extra effort to contact me personally.
I hope some of these suggestions are useful to you! Maybe other teachers will have better ones too. Good luck with DD's school - I hope you all have a wonderful time!