And though I have...all knowledge...and have not charity, I am nothing. (1 Cor. 13.2)
Knowledge is good, but knowledge with virtue is most greatly to be sought for our children.
C.S. Lewis once wrote: "Education without values, as useful as it is, seems rather to make man a more clever devil."
Martin Luther is likewise quoted as saying, "I am afraid that the schools will prove the very gates of hell, unless they diligently labor in explaining the Holy Scriptures and engraving them in the heart of the youth. I advise no one to place his child where the Scriptures do not reign paramount. Every institution in which men are not unceasingly occupied with the Word of God must become corrupt."
It is worthwhile to quote him in greater context from his 1520 Address to the Christian Nobility of the German Nation (§25):
But where the Holy Scriptures are not the rule, I advise no one to send his child. Everything must perish where God's word is not studied unceasingly; and so we see what manner of men there are now in the high schools, and all this is the fault of no one but of the Pope, the bishops, and the prelates, to whom the welfare of the young has been entrusted. For the high schools should only train men of good understanding in the Scriptures, who wish to become bishops and priests, and to stand at our head against heretics and the devil and all the world. But where do we find this? I greatly fear the high schools are nothing but great gates of hell, unless they diligently study the Holy Scriptures and teach them to the young people.
Jacobus Koelman includes a poem about this as well in his classic treatise The Duties of Children, p. 58:
The Child Studies
He who best sifts through what exists,
Possesses wisdom that persists.
A smart parent gives good education,
So his child master's life situation.
But unless he attends the highest school,
Where virtue is learned in the soul
And God's law is kept as a whole,
For all that he learns he'll live like a fool.