I teach, and our school district is very strict about absences. We have a large population of students from poverty, and many of those students come from homes where the parents think nothing of keeping them home simply because the child didn't feel like attending school that day. We also have a decent size population of students from families that can afford vacations, and we often have students missing for vacations.
Between the two populations, our school district loses A LOT of money from the state due to attendance. When they find themselves in truancy court, they holler and pitch fits like four-year-olds in the cereal aisle that the school only wants money. It would be awesome if our funding were tied to something with which we had greater control than whether or not students attend classes, but unfortunately we need every cent. My colleagues and I have had our take-home pay decrease for six consecutive years because the school district cannot afford raises sufficient to combat our risings medical insurance premiums.
With the revenue down, our pay goes down, the budget for materials goes down (and we end up purchasing those materials from our own pockets--with our shrinking take-home pay), and parents accuse teachers of being "bad, uncaring teachers" when they do not use their personal time after work to compile work for the child leaving for vacation and for not wanting to deal with the red-tape of a grade change when the work isn't turned in on time.
I would LOVE to take a vacation during the school year. I see the benefits so much. Lower crowds. Lower cost. A nice break in the middle. Our family would love to do it. Even if the school district would hire a sub for me to take a vacation (they won't), my children would not be excused for the days missed. And I know that their teachers would not be required at all to give the make-up assignments for their unexcused absences. And of course, there is all the class subject content they would miss. That's the biggest concern, really. They can overcome a few zeroes; they can't magically know material that they haven't been taught.
Our school district has recently adopted a different calendar, and I'm hoping it makes a difference in attendance with our vacationing students. We will attend school for a greater portion of the summer, while having a bit more time in the winter and spring.