So you mean to say kids are impressionable? No shit! Go figure. And we know what the "K" in "Pre-K" stands for, right komrad?
All States or organizations, or at least most, try to get the children. That was the reason for public education as first practiced (in modern times) in Prussia whose system we adopted (with some Dewey and Skinner thrown in for good measure.) This has been going on forever. As I mentioned for good, or for ill. But, generally, get the children as early as possible and they can be molded.
As a side-benefit, especially for those of a more socialist bent, you also help undermine the family structure which is always a key goal as the nuclear family helps reinforce the patriarchal, capitalist system where womyn are seen as simply a unit of production. The nuclear family was created by the capitalist system and class-society and was preceded by "primitive communism" (or to use another term by a more Fabian adherent: "it takes a village") hence the need to break down this modern phenomena and early schooling, in addition to other things (like redefining marriage, easy divorce, promotion of homosexuality, gender-bending, political correctness, and undermining other institutions that block our progress to the eventual utopia, etc.)