We have taken our kids out of school for vacation many times over the years. We always email all the teachers about a month in advance and then again 1 week before we leave. Only one teacher has ever given us grief about it in all these years. Ironically enough, it was one their phy ed teachers. DD had to come to school early every day for a week to "make up" her gym classes. I had to laugh, though. I'm pretty sure she got way more physical activity on the excursions we did than she would have gotten at school.
Having said all that, our kids do not struggle academically, behaviorally or socially. If they did, the school might be more opposed to it. Of course, I wouldn't take them out if they were struggling anyway.