The same problem may arise even within states...like ours, for instance.
And just what are we testing on these standardized tests? NAEP (National Assessment of Educational Progress) results for civics show that we're doing badly in that subject as well. But I'm not sure these kind of test items are proof of that.
At least if we all agree on a common core, and we develop some sort of common assessment of that core, and we apprehend the strengths and weaknesses of both, we can talk about students and their performance in something of a common language. That's a good start.