Fact vs. Opinion
I don't know how universal it is, but Oklahoma Social Studies Standards currently include Facts vs. Opinions as an essential skill and test over this as part of the U.S. History End-of-Instruction Test. We can debate the value of this, but it is so.
Because primary source analysis, political cartoons, charts-maps-graphs, and other "skill-based" standards tend to be more interesting and more difficult, Facts vs. Opinions is easily overlooked, or misunderstood. It's not particularly glorious, but attached is one version of the department assessment we use in my world to teach the terminology, practice the skill, and assess - usually all in less than a single class period.
Then we can get back to the good stuff.