Forcing all kids to go to school and forcing all kids to learn are two different things.
As you know, daycare (and, say, crime and accident prevention), training, and cultural/national upbringing are different things, and they work differently, often with contradicting goals and methodologies. Currently we tend to treat "education" as a one thing, but in isn't.
I am all for all kids going to school (unless one can provide a better education), otherwise there would be a disaster of crime and poverty, much alike the one during the industrial revolution. However, what happens inside is extremely far from things which "make sense" both for them, and the society.
I'm not saying there's not vast room for improvement here!
I just don't think that abolishing mandatory education/training/socialisation/what-the-hell-ever is a good idea, and it seems you don't either :)
And how do we get kids who could use it, but from backgrounds that wouldn't bother to educate them at all, into the system?
Mandatory education is a good thing.