The real aim of education is make all of us smarter thinkers. At the core of smart thinking is the ability to understand the world. Ultimately, if you are going to solve new problems or to make effective decisions, you need to have causal knowledge about the world. Causal knowledge is what you use to answer the question "Why?" In order to learn from history, for example, it is important to understand the events that took place, but also why those events happened. Current events are never exactly like historical ones, and so the more you know about these causal factors, the better job you can do of applying knowledge of the past to the present.
Unfortunately, the most common study habits are not that effective for learning to give good explanations. First of all, students tend to study for exams in the day or two before the test is given. That kind of studying does not provide enough chances to help connect their knowledge together to provide long-term understanding of the material. If you are going to study for a test for an hour, it is better to study for four days 15-minutes at a time, than to study for an hour all at once.
Second, students often study by re-reading the material that will be covered on the exam. Obviously, reading the material is important, but the exam will require more than just reading, it will require producing an answer. So, it is important to study by actually answering the kinds of questions that will be covered.
Creating your own explanations helps to guard against what Frank Keil and Leo Rozenblit called the Illusion of Explanatory Depth. Basically, we often believe that we understand the way things work better than we do. That means that students often overestimate how well they are going to do on an exam. They think they are ready when they're not.
When you explain things to yourself, you find the gaps in your knowledge. Practicing for an exam by answering questions quickly reveals the places where you learn more. As an added bonus, there is a real benefit in memory for information that you produce yourself over information that you just read.
Finally, tests in schools (and particularly the kinds of high-stakes tests that are used to evaluate student performance) give questions that have a correct answer. And in some domains, there really is a correct answer (or at least a best one). When you add 1 and 1, you better get 2. And the theory of natural selection really is the best explanation for the data on the development of species on Earth.
We have to remind our kids that not every problem in the world has just one answer. Almost every real-world problem has many possible successful answers, whether you're trying to eat a good breakfast, get in shape, or design a better vacuum cleaner. It is crucial that students learn that they are not supposed to find the answer to a problem, but rather to find one or more good answers.