I think parents have to accept that their children will miss something, and it could be important, interesting, different, and not give teachers grief if their children miss out on further opportunities along the way.
However, experience is the best education of all.
Schools give children a fantastic base of knowledge and parents extend this through other means. Schools teach our kids through play, practical maths lessons, first hand experiences of museums, school trips etc and they are all really important.
Family trips can extend children's general knowledge immensely. One example is geography, naming places within the country, seeing the different kind of rocks, soil, and the different colours and textures. A teacher can talk about this forever, but if a child experiences it they are more likely to remember.
A child is taught maths, but if they practice the numbers by using equipment, they are more likely to remember.
Education outside school is just as important. Schools are very important and the teachers work really hard to do the best for your children, but you as parents can also teach them.
I am not suggesting you take lots of weeks out of school, but once or twice can be good for children.
I mentioned below about beach holidays not being educational, but they are very good for developing social skills. Children will meet other children and play with them, and they are in a different environment so their skills of people handling will be practiced and they will learn from this.