A public- school system, in itself, is indeed of enormous benefit to the race. But it is of benefit only if it is kept healthy at every moment by the absolutely free possibility of the competition of private schools. A public-school system, if it means the providing of free education for those who desire it, is a noteworthy and beneficent achievement of modern times; but when once it becomes monopolistic it is the most perfect instrument of tyranny which has yet been devised. Freedom of thought in the middle ages was combated by the Inquisition, but the modern method is far more effective. Place the lives of children in their formative years, despite the convictions of their parents, under the intimate control of experts appointed by the state, force them then to attend schools where the higher aspirations of humanity are crushed out, and where the mind is filled with the materialism of the day, and it is difficult to see how even the remnants of liberty can subsist. Such a tyranny, supported as it is by a perverse technique used as the instrument in destroying human souls, is certainly far more dangerous than the crude tyrannies of the past, which despite their weapons of fire and sword permitted thought at least to be free.
Machen, Christianity & Liberalism, p. 13 – 14.