Schools are usually the biggest tools used by governments to guide their population to a way of thinking. Thats how they massify knowledge! It is rare to find independent teachers who have the freedom to teach what they learned in a very neutral way. I was a teacher back in Brazil, not history, but I know that a teacher in Brazil could have more freedom of teaching different from a dictatorship country where if the teachers goes off the rail can be sent to jail. But even being a teacher in a democratic country you need to follow all the topics that the school and country intend for their student to learn.