It's legitimate (though not necessary) when it plays a subsidiary roll assisting parents who are the primary educators of their children.
"The way to have safe government is not to trust it all to the one, but to divide it among the many, distributing to everyone exactly the functions in which he is competent....To let the National Government be entrusted with the defense of the nation, and it's foreign and federal relations..... The State Governments with the Civil Rights, Laws, Police and administration of what concerns the State generally. The Counties with the local concerns, and each ward direct the interests within itself. It is by dividing and subdividing these Republics from the great national one down through all it's subordinations until it ends in the administration of everyman's farm by himself, by placing under everyone what his own eye may superintend, that all will be done for the best."
Thomas Jefferson