It means being prepared to use political rights such as voting and freedom of speech. It means being responsible for your own life, finances, and social interac

It means being prepared to use political rights such as voting and freedom of speech. It means being responsible for your own life, finances, and social interactions. And other things like that. When a kid turns 18, they suddenly have many rights and responsibilities. The primary purpose of education is preparing kids for those. A 18-year-old has typically spent 20-25% of their waking hours in formal education, depending on what you count. That's a substantial fraction of their life so far. Formal education is particularly important for less fortunate kids who don't learn many useful things from their friends and family. If you want such people to have rights and responsibilities, they must be given a chance to prepare. Otherwise the society will suffer.