What I am annoyed with is that it is OK for for children to go away on a skiing holiday with the school but it isn't ok for them to go away on skiing hols with their family.
Now, as far as I'm concerned, this is the same thing. A week of hols out of school hols. Not all dcs will go, far from so the others will still do some work during that week and the ones away will have to catch up or is it that they expect the ones not going to wait for a week for them to come back so they start learning again??
Tbh, as parent, I really don't care about the attendance level of the school and the impact on their Ofsted report. I do care about my child being able to learn appropriately. Learning doesn't always happen at school to start with. But more importantly, to make a fully rounded individual, you need much more than good enough academic results. Sometimes, spending a week with your family is much more important for the development of the child. They do accept that for a child who is doing some sport at a high ish level. so why is to not OK for nurtuting relationships?
I DO however think that some people take the piss. A child in my dc years has been away for two weeks, right at the start of Y7 (ie the worst timing ever) to be at his dad's wedding ... in Cyprus. That was deemed acceptable apparently 
And yes, if you have a child that has already been off for 2 or 3 weeks following a couple of illnesses, taking then out for some hols might not be the best thing for them. (And even then I can think of some circumstances where actually this could be exactely what the child needs).