The word "democracy" originates from the Greek words "dēmos" and "kratia" which mean "people" and "power," respectively. Simply put, the word – from its original use – has always been associated with the idea of giving the "power to the people." To that extent, one of the most major democratic ideals has been to have a society where the populace is effectively capable of playing its major role in the government. The question of course arises, "how does a society achieve that capable populace?" .
To refer once again to the Greeks, that answer lies in education. The Greeks had mandatory education for boys up until the age of 14. Afterwards, most were sent off to study under skilled artisans, philosophers, or politicians. ("Ancient Greek Education") There they would learn how to become full participants in their society. Thus, starting with the Greeks and moving onward to other major societies throughout history, education has been a major societal foundation. In fact, it was such a major foundation that in 1852, the Massachusetts House of Representatives made education required for children from ages eight to fourteen (The first state to do so in the US). Although this mandated education wasn't passed to ensure the success of government, it was passed to ensure the proper formation of children to become full members of society (Massachusetts).
From Massachusetts, compulsory education spread across the land for a similar reason – education ensures that we, as a nation, have a populace that shares ideals and goals. This compulsory education is still upheld for the sake of the nation, so that we might have an educated populace capable of voting and being good, active participants in society.
Yet, as people look at the state of our modern school system and our government, they wonder whether or not compulsory education is working the way it has always been intended – to create the educated populace.