This is certainly an area where the schools are tightening up.
My three kids are now 20, 15 and 14 and the rule when they were all much younger from the school was along the line of 'family holidays up to two weeks will be approved'.
This changed a few years ago, and we had to jump through a few more hoops, but the school still allowed it if the timing was sensible (ie. a week tacked on to the end of half term to make two weeks).
However in recent years, it has become a flat no, with penalties in place if you do.
So we did take our kids out of school for holidays when they were further down the school, but it has been at least 5 years since we last did that, and there is no prospect of doing so in the future.
Did we do the right thing? In hindsight, and fully accepting the hypocrisy of the situation, I'm going to say a qualified 'No'.
My wife has worked extensively in both primary and secondary schools as a Maths specialist, so I'm basing this on her experience and feedback.
The kids in primary school learn at such different rates and ages, especially in the earlier years, that there is always a good degree of re-work going on in the classes, so it's not a big deal if one kid is two weeks 'behind' the rest - this is always going to be the case anyway. That said, if the school thought it was not appropriate, I'd support their decision.
Secondary school, with streamed classes, this just does not work - the group do need to move forward as a group and concepts are layered, so it is a real pain when people get of our synchronisation. Now it happens for reasons other than people buggering off to soak up the sun for two weeks, but let's not make it any worse than it needs to be.
In so far as engendering the belief in your child that any rule they don't like can be dismissed, that's just a bit too simplistic. Schools need conformity in order to function, rules provide conformity - you might not like it, but that is the reality in today's sausage factory that is our education system. Scoring 'one for the man' by supporting your child's right to break free of the shackles of oppression may sound ideal, but in reality, it's just selfish.
We've seen plenty of examples where mummy and daddy's little prince or princess is too precious to follow the 'rules' for fear of crushing their burgeoning individuality. The current guidelines in force at my wife's place of work is to remove all the well behaving pupils from class when one of the more troublesome darlings plays up, so as not to give the disruptive pupil negative attention, while removing their audience. It's bloody stupid.