It's not a single agenda. People have different ideas and methods to achieve noble goals. Some of the noble goals may coincide, though.
People convinced that what they teach at school is the truth want to spread it. They want to help other people, who have lost the truth and started believing in telekinesis, conspiracy theories and the like. In their eyes, it's all lies and they don't want other people to believe in lies.
People convinced that in order to make the world better and more peaceful we ought to skip nasty events in the history books, they want to help other people understand this too.
People convinced that they're not teaching the truth at school, want other people to realize that too. They stand against government-regulated school systems and they stand for home-schooling.
Some people are convinced that 12+ years of forced education degenerates the creative mind. They want to help the world by promoting a change in the education system, which would allow for more creativity in learning.
There's at least a dozen more viewpoints at school and education.
I guess all in all, education because people.