Every family has to make their own decision. IF your kid is doing well, and IF the week you want to take doesn't have some important school event/project/test that your kid will miss and can't make up, and IF the school/district won't hassle you for it...then it's fine.
This is what my parents did. My brothers and I were pulled from 2nd (me), 6th, and 8th grades for 1 full week in October of '83 to go to Disney World. I asked my mom about it a few weeks ago, asking her if the teacher or school gave her any grief about it. All of our teachers thought it was fine, and made up packets of work for all of us to do (and we did them, every night after the parks and before we could go to the arcade room at the CR). We all came back, handed in the work, and didn't miss a beat. I even did show and tell about my trip.
All three of us are well educated adults today, and I can't be certain, but the missed week didn't hurt us when applying for college (but none of us tried for Harvard, either!).
And you know what? That vacation gave me some of the best memories of my life! My dad worked weird hours and we couldn't always see him, much. Our family vacations were the most time we ever spent with him until he retired a few years ago. It was time much better spent on Space Mtn. than learning fractions that week.
I DON'T approve of taking a kid out for more than one vacation a year. I remember classmates of mine that would always start the school year a week late, be taken out early for winter and spring breaks, and not show up the last week of school, almost always because of family trips (I lived in an upper middle class neighborhood, lots of rich kids went to my schools who could-and did-travel a lot). This is way too much interruption to a kid's schooling, and DOES teach the kids that trips are more important.
I also feel that pulling a kid out of high school is too difficult, between multiple subjects and teachers, plus activities.
But once a year, or once every couple years, is fine (again if the criteria from my 1st paragraph is met!) for grade schoolers. It's just not THAT big a deal, folks!