Haven't read all the responses, but here's my two cents. BTW, I am a teacher too - 3rd grade, which is a testing grade here in TX.
When our kids were little (and I was a SAHM) we loved going to DW off-season. When my older two were in 1st and 2nd grade, they had a fall break - we decided to go for 2 weeks (free dining!

) and piggybacked the school break - it was not a big deal, and they kept travel journals that they shared when they got back. The next year, we went for Fall Break again (alas, the last one, since they discontinued that holiday!

) and bought
DVC. DH wanted to go soon, so we booked a trip for DD's b-day in June. Kids were in K, 2 and 3 - and I was teaching again. This time it was still no big deal for the kids, but it was a beating for me - sub plans for a week, and then catching up when we got back. It was a great trip, and worth the work, but I said never again.
However, when we took our first
Disney cruise last Christmas, we were hooked - and decided to rebook. Cruising during school breaks is way more expensive, so we booked for October 2010. We will have to take the kids - and me - out of school. They will be in 4th, 6th and 7th - older two in MS. I am nervous about it, but since it is in the fall, it should not affect testing.
Our school district is pretty tolerant of travel. We have a lot of different cultures in our area, and many who have emigrated to the US. To visit family in their home countries, they often have to take long trips at unusual times. I have had several children miss weeks of school to visit family in India, Ethiopia, Peru, and other countries. I would never want to deny them these opportunities. These children are usually good students and plan in advance to make up work. I usually just send them with some math work, books to read, and a Travel Journal I make up for them.
This will probably be the last time we will take the kids out. Our kids are very good students, and we will not have trouble getting caught up, but as they get older and more involved in school activities, sports, etc. I know it will be harder to miss school. We have reconciled ourselves to going to DW - and other places - in the summer, but we could not pass up the chance to take another amazing Disney cruise at a reasonable price!
By the way, I know not all teachers can take time off - we are limited to 5 at a time unless sick. We are given 9 days a year and can bank unused days, which I do. Fortunately, DH has a flexible work schedule and can stay home with sick children and I have not had to use my days unless I was sick or for personal use. However, we are not allowed to take days off before/after a holiday unless sick. I even had to call in "sick" when I took off a Thurs/Fri that fell before a Monday in-service.
As pp stated, it is a personal decision that must be based on the child, the school, the teachers, the family circumstances, etc. I think family vacations are some of the best learning experiences children can have. Some families simply can't travel in the summer, some experiences are more expensive in the summer/spring break.
Good luck to all making these decisions! My kids know that I value school, but I want my "message" to be bigger than that - that I value time with them, and that getting away from everything is sometimes the best way to enjoy each other!
