Term time holidays were in last week's papers again. The headline in the Sunday Times was; "No causal link between term time holidays and academic performance." However, when you read the story, what the researchers said was that the data was contaminated by absences for reasons other than holidays and therefore no hard evidence could be concluded, Not exactly the same thing as 'no causal link'.
It's simple common sense that absence from school, whatever the cause, will have some effect on learning if no remedial steps are taken. The effect will lie on a continuum - no school at all and you wouldn't expect good academic performance; a perfect attendance record in itself does not guarantee a good performance, but it would guarantee a better performance than no school at all. If the pupil concerned is diligent and catches up, then yes, there will be no effect.
The problem as I see it is that parents who put holidays before school, for whatever reason, are generally the kind who don't place a high value on education. With that kind of millstone, the child is, unfortunately, unlikely to be academically inclined in the first place.
I would never dream of taking my child out of school for a holiday, unless it was justified from the perspective of adding to their overall education, and even then I'd have to think very hard about it. Sitting on a beach in either Benidorm or the Maldives adds nothing to a child's education, whereas touring the Prada Museum or being forced by their parents to speak a language they are learning with locals in the holiday destination will. That said, that can be done outside of term time.
If you can't afford a foreign holiday in the peak season, then rein your expectations. A foreign holiday is not a human right. Your child's education is infinitely more important.