|Article III of the Northwest Ordinance requires:
Religion, morality, and knowledge being necessary to good government and the happiness of mankind, schools and the means of education shall forever be encouraged. 
"Religion" means "Christianity"
What does "knowledge" mean?
Not just "the three R's" (reading, writing, arithmetic).
Reading is not the goal; it is a tool to gain knowledge. A colonial American who could read but had no "knowledge" was a failure. (Today's school children don't even know how to read.)
"Knowledge" means an understanding of how God's world works, and our place in it, so that we can discharge a lawful calling.
Providence + Capitalism vs. Mercantilism/Socialist Central Planning
Students in secular schools do not understand how God's World works. They do not understand "providence." They could not explain how an "Invisible Hand" orchestrates human action to produce the goods and services we live on.