i took them out for 3 weeks one year....
up to that point i had been really rigid about never taking them out of school, but it was the last chance before DS (12 years old at the time) was about to move up to a school that i knew he could never miss, so i figured what the heck, may as well go for it..
i took them out just before thanksgiving, so that we could first go to my sister's house in michigan for her big thanksgiving feast (and i do mean feast)..
then we went to WDW for 3 weeks (end of November and first 2.5 weeks of december, so it was relatively quiet there), then back to michigan for one more week so the kids could see some snow (alas, michigan had a freakishly warm winter that year, so no snow until the day of our flight - the day before Christmas)..
anyway, when i came to the head of the school to tell her that DS would miss 3 weeks, she said she couldn't authorize it..
i told her i wasn't asking for permission, i was just coming in to inform her that he wouldn't be there for 3 weeks...
she was a bit stunned, but i wasn't about to take no for an answer...
it was the only time we ever took them out of school and it was definitely worth it.......it was a very special trip....
and considering they're now 27 and 24 years old and very successful, it would seem it didn't have much impact on them