I teach a lot of kids who, by Jerry Pournelle's definition, can't read. Oh, they can usually make out most of the common words, which allows them to muddle through their "grade level" reading assignments without much trouble. But if you hit them with a longer word - like, say, "discrimination" - they're instantly stumped and need to ask me for its pronunciation. I also teach a lot of kids who are basically competent readers on the decoding and fluency level but have trouble processing and understanding meaning. These are the kids who will read that a scientist "uses the data she collects to analyze the greenhouse effect" and erroneously conclude that said scientist has somehow fixed the greenhouse effect.
The kids in the first group have a problem that is relatively easy to solve. They are, evidently, victims of incomplete, incompetent, or absent phonics curricula and are consequently unable to break an unfamiliar word down into its component pieces. The cure, quite simply, is to explicitly teach them the word analysis skills they are missing. Beyond "b says buh," students also need to know that "-tion" says "shun," "ph-" says "f-," and "-ough" says "-oh" in some cases and "-uf" in others. They should also learn where these words come from; if a child knows, for example, that a word has a Greek origin, that's a big hint as to how it should be pronounced (and spelled). And they should learn common prefixes, suffixes, and roots, which will allow them to decipher the pronunciations and meanings of a whole host of more obscure terms.
The kids in the second group, on the other hand, have a more difficult - and, it seems, more common - deficiency. They are prone to making wild, illogical leaps while reading a passage about the greenhouse effect because, quite frankly, they don't know anything about the greenhouse effect -- beyond, perhaps, some vague suspicion that it has something to do with climate change (which, they've dutifully absorbed, is a bad, bad thing). They don't know that, for the most part, it's good that our nice, thick, substantial atmosphere can trap thermal radiation from the sun -- that without the greenhouse effect, the ambient temperatures on Earth's surface would not be so conducive to the development and maintenance of life.
We comprehend best when we can use prior knowledge as a scaffold; this is the solid finding of cognitive science and also a conclusion backed by common sense. I am an expert reader, by and large -- but if I took a test that included, say, my co-author's masters thesis on atmospheric wave packets, my typically high scores would no doubt plunge, as my background in earth science is surely inadequate for such a task.
Now, of course, most of our students aren't going to go into climate research and therefore don't need a masters-level understanding of atmospheric mechanics. But in order to read and apprehend materials published for the general public (as opposed to technical experts), kids do need quite a bit of basic scientific and cultural knowledge. Why? Because most writers assume that basic knowledge. They have to, or their prose would be turgid and, quite frankly, unreadable. Can you imagine what would happen if, instead of simply saying "Tom had the patience of Job" and being immediately understood, a writer had to add "who, by the way, was a person in the Old Testament who lost his livelihood and his good health and yet still maintained his faith in God"? Good Lord! All of our books would be thousands of pages long and would weigh fifty pounds a piece!
Unfortunately, a lot of my students have been inadequately exposed to our cultural patrimony, so the above-mentioned shorthand leaves them completely lost -- even if they can decode every single word in the sentence "Tom had the patience of Job." The reasons for this are legion, but I think one major contributing trend is our education establishment's anxious desire to teach things that are "relevant" to our students. "Kids won't be interested," so the thinking goes, "if the material doesn't somehow apply to their own lives." But this is 180 degrees opposed to reality. In reality, kids are naturally curious about things that go far beyond their everyday experiences. Remember the sixth grader I mentioned a few articles back who went ape over the word "Brobdingnagian"? He's also recently developed an obsession with Greek mythology, a topic thousands of years removed from his 21st century existence. No -- youth fantasy writers would not be making out like gangbusters if kids weren't looking for ways to expand their horizons. Teach a bunch of seven-year-olds about ancient Egypt and they'll jump all over it -- provided you present it as a story and not as a list of discreet, tedious facts. It also helps to take advantage of innate peaks in student interest. First grade is a good time to introduce biology because children at that age - especially the boys - are endlessly fascinated by critters and beasts -- and the tween years are a good time to do some basic chemistry and physics because kids then become interested in building things (and, in many cases, blowing them up).
But once again, I digress. Here's the bottom line: If you are a parent (or a future parent) who wants to raise a proficient reader, there are two principal things you must do. First, you must teach your child phonics! Phonics is an indispensable first step for beginning readers; without it, they will always depend on others to sound out unfamiliar words and will never become self-sufficient. Secondly - and even more importantly - you must provide your child with a knowledge-rich and word-rich environment. Leave plenty of time open during the day for free reading -- and reading aloud. Go on nature hikes. Go to the library. Go to museums (most of which are free or pay-what-you-can). Watch high quality educational programs. Don't hothouse your children and drill them with flashcards (unless you're going over the arithmetic tables); do take advantage of their built-in tendency to ask questions about the world and how it works.
Literacy, in my experience, requires cultural capital. Provide that capital, and your children will do well.