I see the unschooling philosophy as saying that school is not necessarily more valuable than a large variety of other things you could be doing with your life, therefore you don't need to force your kid into it.
Sometimes I see some articles about unschooling that don't bother to explain the difference in mindset. (I think they're usually written by people who aren't unschoolers.) People who believe strongly in schooling see these articles and seem to understandably get the impression that unschoolers honestly believe that their child, at age 8, will come to them and say, "Mommy, please teach me multiplication, since I will need it to get into college 10 years from now, which I will need to get a job and support myself someday." And yeah, that's not happening!
Those people hear unschooling called "interest-led learning" or "child-led learning," and they're picturing traditional homeschooling where the child chooses their own curriculum. (To make matters worse, they're probably picturing homeschooling as more school-like than it actually is.) In their eyes, unschooling fails if the kid doesn't pick the same thing they'd be taught in school.
I think these are some beliefs pretty much any unschooler shares:
1) If it exists in the real world, you can learn it in the real world. If it doesn't exist in the real world, it's okay if you don't learn it.
2) Nobody wants to be forced to memorize things that are useless to them. Kids are happy to learn things for the fun of it or to achieve a goal they have set for themselves. And sometimes they just learn things by accident.
3) It doesn't matter what age you learn something. If you get to age 18 and are bothered by the fact that you still don't know your multiplication tables, you can just learn it then.
4) Sometimes you do need to be learn things in a certain order, but it's not nearly as common as many people think. For example, you don't need to memorize your multiplication tables in order to take a calculus class.
5) Kids can and deserve to learn things the way adults do, e.g. you need or want to know something, you go find out about it.
6) There are a few things you need to learn by the time you reach adulthood if you're going to succeed in adult society, but the list is much smaller than schoolers act like it is. (And half the stuff on it isn't taught in school anyway.) You're not a failure of a human being just because you've never read the script for Romeo and Juliet, for example.