I can give a very simple example - in my high school history class, the cold war was presented as a conflict between communism and democracy - despite the fact that on an economic field the conflict was clearly between communism and capitalism, while on a political field proponents of both systems were happy to subvert the democratic process whenever someone had the audacity to vote for the wrong economic system.

Ooh, as I was typing I thought of a better example - remember the four food groups? eight to twelve servings of grains per day? Less obviously propaganda, though I'd argue the farm lobbies pushing it count. But harms in terms of its link to obesity and heart disease are pretty damn stark.

Given that school children are a huge captive audience of future consumers/voters/employees it would be incredibly strange if the curriculum wasn't the target of all kinds of special interest groups that aren't perfectly aligned with public interest.