After reading all 22 pages of this, wow, I didn't realise how hot a topic this could be. Or how different it is down in the US.
I'm not going to say what people should or shouldn't do. I will speak from my own experience though as one of those children who were taken out of school for family vacations.
I went approximately 14-15 times (3 times in one year because we had annual passes) prior to entering University with 1-2 of those trips being in high school. All the rest were ages 13 and under. We did some trips over the pre-scheduled holidays (Christmas, March Break, etc.) and we did one in June for my grade 6 graduation. One trip in June was enough, due to weather more than anything else.
I wasn't an amazingly bright child. I was good at some things, not so much at others, like any kid. I remember some of the specific lessons I was taught in school, but it's mostly just clips here and there.
I do remember almost every trip I took with my parents. I remember fun times with my Dad before his heart attack, inside jokes he and I will share forever. I remember finding rides my Mom would ride that my Dad wouldn't even though to me he was not scared of anything. I have albums of pictures of me at Disney, hugging characters or other random acts (I apparetly loved dancing to the theme music in the World Showcase...

).
I have had so many wonderful memories there that WDW became my 'happy place' when things get hard, and they did.
Would I take my future kid(s) out of school for Disney? Yes, I probably would. I would probably try to do it in the way that least impacts everyone involved (aim for the school breaks, etc.) but I know how much those trips mean to me and how many wonderful family-filled memories I have there. I gained much more from them than I would have from a few more days in class.