"A primary purpose of the educational system is to train schoolchildren in good citizenship, patriotism and loyalty to the state and the nation..."

From Townhall.com
This is the primary, the deliberate purpose, for Govt schools. More important from an eternal standpoint is you are trained to view everything through humanistic eyes. They actually accomplish this more thouroughly.

Threat to Homeschooling
By John Stossel

The cat is finally out of the bag. A California appellate court, ruling that parents have no constitutional right to homeschool their children, pinned its decision on this ominous quotation from a 47-year-old case, "A primary purpose of the educational system is to train schoolchildren in good citizenship, patriotism and loyalty to the state and the nation as a means of protecting the public welfare."

There you have it; a primary purpose of government schools is to train schoolchildren "in loyalty to the state." Somehow that protects "the public welfare" more than allowing parents to homeschool their children, even though homeschooled kids routinely outperform government-schooled kids academically....read it all