It is one of the major failings of our education system. Our schools are so focused on "teaching to the test" they they fail to teach proper skills that actually help students learn rather than memorize. This isn't the fault of the teachers but rather the bureaucracy in charge of it.
These days, Teachers appear more concerned with how their classes' performance reflects on them, Rather than if the students are actually learning something. Many kids who Ace a class, Leave learning less about the content than how a teacher tests, Or how exams are structured. Study sessions are too often just the teacher providing answers to the tests and practice tests are just reworded variations of the exam.