With politics comes bias. Whether conservative or democrat it is hard to discuss the issue without leaning one way or the other, making it difficult to share information about political events without swaying the audience (classroom full of children). This is an opinion based in personal experiences. I could be wrong.
At the student level they need to be kept out because students need to form their own opinions based on provided unbiased information, they shouldn't be guided. At the government level politics need to be kept out and educational policies that serve the greater good need to be put into place as opposed to two sides blocking proposals from one another "because that's what you do."
Brainwashing a child to be conservative or liberal is against the idea of freedom in education. But teaching debate, creative thinking, and Sophist-like speech are good techniques for kids. Many of them will be in public office some day, so it is important to give them skills. If there be a bent, it should be to promote bipartisan ideas.
Of course we must then rely on each teachers good judgment when it comes to being careful not to persuade any particular political leaning, but young people are soon going to be asked to participate in the political system and they must have a good understanding of government and politics to be able to make sound decisions. We cannot be certain that they will get unbiased information anywhere else.
Politics need to be involved in education to ensure public schools are meeting regulations. Also, removing politics from education would mean abolishing public schools completely - how can you have a government organization with no politicians involved? This would mean a society of private schools with very differing levels of education, and the inability of some children to even attend school.
I feel that even more so today, our students should understand our political system, the various types there are in the world, the pros and cons to each type and how they affect us now and in the future. A high school student is only a few years away from being able to vote, and the better educated, the more intelligent an electorate we will have. The key is to not push upon the students any particular philosophy, but to provide them with a well rounded overview of the system.