I think the point of history teaching in schools and universities is to try and get young people to form their own opinions about the past and historical figures. Encouraging their bias in a way, and encouraging them to find reasons to support their view of the past. For instance, when I was in school I thought that Gladstone was an idiot. My teacher challenged me to produce some evidence for why I thought that he was an idiot, his quite rigid Christianity, his tentative support for the American south during the Civil War (later recanted) etc. and in comparison to Disraeli I judged him to be a somewhat lacklustre politician. He basically rubbed me up the wrong way. Now, while I was right on my facts it was pointed out to me that my observations only made up a very one dimensional portrait of a man who managed to hold the Liberal party together in the 19th century. My point is that my bias and having it challenged led to me forming a more nuanced view of a historical figure, even though I retained my instinctive distrust for him. I hope this does not violate the personal anecdote rule.
As for government and government education policy.... that's a whole different question. My honest answer is that no person or group of people can completely remove their agenda from a topic. This will shape the content of the material (the inclusion of women for instance), the way it is presented (The conversion of Edwin for instance could be taught as pious conversion or a cynical attempt to associate himself with Roman power (or both)) and will almost necessarily be affected by nationality (Trafalgar will be remembered as a huge victory for the British by the British and a defeat for the French by the French, if it is taught at all in schools). While i would love nuance to be taught in schools, which would inform the students about the agenda of the people who set the curriculum, almost all places below university level are not capable of this. Just so long as the agenda is not gratuitous (for instance teaching that Germany's hyperinflation of 1923 was the work of the Jews, I could link more recent examples but 20 year rule) I don't see why we should attempt to excise agenda from schools.
By teaching students that history is not a series of events to be memorized and then later used to justify political beliefs.
The problem with most "historians" is that they start with a political bias and simply find historical anecdotes to support them. This is backwards in terms of scientific methodology where conclusions must flow from repeated observation. Indeed, many historians nowadays do the equivalent of claiming that all elephants are white because they found one white elephant; rather than looking at all of the elephants and realizing most of them are grey.
History, practiced properly, is instead an ongoing process of investigation - where observation of a large subset of human actions will reveal patterns of behavior that give insight into human nature. People are fond of saying that those who ignore history are doomed to repeat it. I would wager instead that it would be truer to say that people repeat history because human nature has remained fundamentally the same since the dawn of civilization; and that history is a tool for learning about human nature.
Unfortunately, the frank reality of the American educational institution is that it has become lazily obsessed with standardized testing - wherein memorizing and repeating historical "Facts" (which are very often myths - see the excellent book "The Lies My Teacher Told Me") - is lauded over analyzing history and searching for the aforementioned patterns.