This would not be a problem if someone had taught them the meaning of the word essay.
Translation: The test isn't valid because the teachers are incredibly incompetent.
From Merriam-Webster Collegiate dictionary:
essay - 3 a : an analytic or interpretative literary composition usually dealing with its subject from a limited or personal point of view
essay question - an examination question that requires an answer in a sentence, paragraph, or short composition
I'm not sure I see your point about the meaning of "essay."
It appears this was a test of the ability of state education administrators to write a coherent question that elicited the desired type of response. They failed. The teachers did not see the question until the moment they gave the test to their students.
My understanding is that an answer that expounded upon a single point was scored high, while an essay that listed several points was scored low.
I suppose for most fourth-grade students a "great day" in school requires several pleasing events, not just one.
Beware.