Here's what the lower court had said was the reason for the law:
The salutary purpose of the statute is clear. The Legislature had seen the baneful effects of permitting foreigners, who had taken residence in this country, to rear and educate their children in the language of their native land. The result of that condition was found to be inimical to our own safety. To allow the children of foreigners, who had emigrated here, to be taught from early childhood the language of the country of their parents was to rear them with that language as their mother tongue. It was to educate them so that they must always think in that language, and, as a consequence, naturally inculcate in them the ideas and sentiments foreign to the best interests of this country. The statute, therefore, was intended not only to require that the education of all children be conducted in the English language, but that, until they had grown into that language and until it had become a part of them, they should not in the schools be taught any other language. The obvious purpose of this statute was that the English language should be and become the mother tongue of all children reared in this state. [citations omitted]
And, here's what the Supreme Court said in reversing the Nebraska court on constitutional grounds:
The desire of the Legislature to foster a homogeneous people with American ideals prepared readily to understand current discussions of civic matters is easy to appreciate. Unfortunate experiences during the late war and aversion toward every character of truculent adversaries were certainly enough to quicken that aspiration. But the means adopted, we think, exceed the limitations upon the power of the state and conflict with rights assured to plaintiff in error. The interference is plain enough and no adequate reason therefor in time of peace and domestic tranquility has been shown. ... As the statute undertakes to interfere only with teaching which involves a modern language, leaving complete freedom as to other matters, there seems no adequate foundation for the suggestion that the purpose was to protect the child's health by limiting his mental activities. It is well known that proficiency in a foreign language seldom comes to one not instructed at an early age, and experience shows that this is not injurious to the health, morals or understanding of the ordinary child.
Every period of immigration has resulted in the same cycle of fear, ultimately unnecessary and ham-handed attempts at forced assimilation, and legislative isolationism.
As Santayana said: Those who cannot learn from history are doomed to repeat it.
What's next ... shall we repeat the experience with internment of the Japanese?
How many more apologies will future Virginia legislatures need to offer?
"We are made wise not by the recollection of our past, but by the responsibility for our future." George Bernard Shaw