Think about it: what's the purpose of a test? I'm sure there's a technical definition, but I'd define it as a method of measuring something. In this case, the test is measuring how much students know and, by extension, how effective the entire district is when examining larger sample sizes. (We can debate whether or not the Keystones are accurate tests, but that's the theory). What, then, is the purpose of "test prep"? It's likely to make a student do better on a test. Better than what? Better than that student actually is. In other words, test prep is all about artificially increasing test scores in the final minutes to make students and the school look better than they are. This is akin to stuffing your face before the beginning of a weight loss challenge and then dehydrating yourself before the final weigh-in. You're artificially giving yourself a momentary edge in order win the game.
Now, someone might say "yes, but athletes train for events and students study for tests, surely test prep is no different!" I would argue that they're half right; students "studying" for tests is just as unethical as test prep. As for athletes, they train because athletes are trying to win. They're in competition with their rivals and it's important that they be better. Perhaps their rival is time, or another athlete, or another team, but their sole purpose is to win the game. Students and learning, however, aren't about "winning". So many artificial competitive constructs have been created in education that students are treated like athletes and being asked to stuff their brains with temporary information in order to appear better than they are in hopes of "winning" a specific test. That might fool the testers...but ultimately that's not the point of school. Now we're simply left with students who are still at various levels of uncertainty...and our tests are meaningless at determining who actually knows what. If we test prep our students so that they all "win the test"...then what? We still have no idea what they actually know, and really no clue how or what needs changed. The same goes for students who cram for exams. They might get a momentary "A", when in reality they only have "C" level knowledge committed to long-term storage.
I can't imagine this will stop anytime soon, but it's an interesting thing to consider. Perhaps test-prep is actually unethical. Perhaps if all tests were viewed as formative instead of summative competitions, maybe they'd actually be useful for a change. Perhaps by putting so many resources into test-prep, we're the ones actually harming our kids, not the invisible monolithic department of Ed.