We need to remember the average adult only reads at a 6th grade level... Not that that's good, but I'd say there's many other factors involved than just the schools (parental involvement, do they read outside school, etc)
And it's not passing the buck to the parents; we're not asking the parents to teach them, merely to be involved, take an interest in the kid's education and show them the value of an education and encourage them to do the stuff they learn outside. The school can't do it all, nor should it have to (I'd argue teachers are already doing a lot more than they were ever trained to do because parents often don't have time to do it in our current society).