(Leg-iron has a long post on education, most of which I broadly agree with. It's not especially relevant to this post of mine, but it's worth a read.)
If government ever understood the purpose of education it has long forgotten it. And it is probable that the state never did know or care why it was a good thing to make sure children were educated. (Or even what education is.) Governments have always used education, as they use everything else, to defend their own interests. (That is only to be expected, since it's what we all do, but it means that we need to make sure that the government's interests coincide with our own, and the People are not very good at bringing it about.)
The early presence of the state in education was intended to compete with the church, or in some cases with other private bodies that were getting too powerful. It has at times been used directly as an excuse to increase taxation, and it has for decades been an idealogical tool controlled for the purpose of indoctrinating the young. Everyone is constantly trying to indoctrinate the young into having one or other set of beliefs, moral principles, traits of character, strengths, weaknesses, philosophical handles, etc, and the state often loses the struggle, but it doesn't stop trying, and education, real education, is lost along the way.
So what is the point of education? What is it that someone, whoever, should be doing for children?
It is generally agreed that the main idea is to prepare them to take their place in the world. What that place is depends partly on the world and partly on the child, which in turn depends on the formation they have received. Children need to learn basic literacy and numeracy, but that won't get them far on its own. They need to understand the world they will be taking their place in, they need to be physically strong, to have strength of will, intellectual curiosity and the analytical tools to satisfy that curiosity. The world needs them to be able to contribute to making it a better place, and they need to be able to make a living, with as many options as possible, and to be happy and fulfilled. The last one is notoriously tricky, but I think we can be certain that filling their heads with rubbish, exhorting them to know their place, pandering to their (quite natural) indolence, and generally depriving them of any real knowledge, enthusiasm or aspiration is not the way to do it.
The ten or twelve years that children are in full-time education should be sufficient to achieve all of these things several times over. If it happened, they would all have to compete with each other, of course, as we do now, and some would win and some would lose, but the world they lived in, and helped to create, would be a much better one for all of them. Yet large numbers emerge knowing nothing, with no concept even of knowledge or ambition or satisfaction, having had their childhood wasted and their future ruined by ideologues, incompetents and tyrants.
I am completely certain that that is not what education was invented for, and it would be an excellent thing to recognize this, and at least try to work out what the real end of education is and think about how to achieve it. But first you have to know how to think, and ideologues don't think, they only believe.