As a Christian, I believe the most important thing that I can teach my children is that God loves them, and that as a result of that love shown to them through the atoning death of Jesus Christ, they can love God and others and ultimately experience what life was always intended to be about. I can achieve everything else as a parent, but if I fail to teach them that exceptionally good news, I've won nothing. I can't control the outcome when they leave my house, of course, but I can do everything in my power to teach them that good news so that it has the best chance of "sticking" even without me around.
It's important that Christians put education, generally speaking, in that context. Some time back I read an article or a book (I can't remember where or I would give proper attribution) and the author stated emphatically that there is no "religiously neutral education". I considered the premise and believe that he was right. The truth is that we will either view the world through the lens of God's existence, so that everything contains traces of his goodness and wonder, or we will view it through some other lens; namely, a lens in which he does not exist. We cannot have it both ways. We cannot say that God is powerful and worth knowing, but unnecessary in relation to the rest of our studies, as if God has nothing to say about writing, or arithmetic, or our basic ability to communicate through words and language, let alone whether or not his existence has any bearing on the universe or why things are the way that they are or why we interact the way that we do. If God is unnecessary for the study of any of these things, then as one philosopher suggested, God may as well be dead. We simply don't need him anymore.
On the other hand, if God does have something to say about all of these subjects, as the Christian believes that He does, then we must approach the education of our children with that conviction. Writing is no longer simply about "grammar", but it is about the wonder that we can even communicate at all, or that we can pass things on to other generations, or that thoughts can become sentences which can become complex arguments or narrative that can be written down and passed on and can create a sense of enjoyment in a person we have never even met. Math is no longer about the memorization of equations or facts but is instead about the way that God has ordered the world so that there are "laws" and "patterns" that always hold true, in every circumstance. Biology is no longer simply about why things are the way that they are, but is instead about what these things tell us about God and his design and plan and wisdom in creating things the way that he did. Studying the cosmos reminds us that things may not always be the way that they seem; that perhaps God used methods and timeframes that we cannot even possibly wrap our minds around in his sovereign control over the entirety of all that is.
I might argue that if we lose the wonder of who God is in the education of our children then it is nearly as serious a flaw as if we forget to teach our kids to love Jesus. That is not to suggest that they are on the same level. Failure to teach about Jesus has eternal implications; failure to view education through the lens of God's sovereignty may just incur temporary boredom. But it is a tragic boredom! It is a similar type of boredom that leads our culture to endure education for the sake of a future promise or paycheck. The type of boredom that makes us stick it out, even though it stinks. To learn math because we have to. To ask the teacher, "when am I ever going to use this?", only to have her give you some canned response about the importance of grammatical construction of a sentence when you are an adult when the teacher knows full well that the answer is, "you probably won't have to use it, except to pass the test."
The Christian can answer the question differently! It's not about whether you "use it". More importantly, what do we discover about God through it? That is the important piece!
This is why education matters for our children. More important than whether or not they memorize facts is whether or not they understand God's purpose in creating those facts to begin with, and then, when we understand them, how we can use them to make a difference in the world.