This is a long qoute from Prof Machen's book, but it is well worth reading all of it.
It might seem as though with such laws obscurantism had reached its lowest possible depths. But there are depths lower still. In the state of Oregon, on Election Day, 1922, a law was passed by a referendum vote in accordance with which all children in the state are required to attend the public schools. Christian schools and private schools, at least in the all-important lower grades, are thus wiped out of existence. Such laws, which if the present temper of the people prevails will probably soon be extended far beyond the bounds of one state, [which will] mean of course the ultimate destruction of all real education. When one considers what the public schools of America in many places already are--their materialism, their discouragement of any sustained intellectual effort, their encouragement of the dangerous pseudoscientific fads of experimental psychology--one can only be appalled by the thought of a commonwealth in which there is no escape from such a soul-killing system. But the principle of such laws and their ultimate tendency are far worse than the immediate results. 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.
J. Greshem Machen
Christianity and Liberalism (1923)