I don't know if the educational system's way of trying to measure student learning is any good. But it faces a tough challenge! It can't look directly into your mind and see the knowledge stored there. It can't surveille your activities and see how much you've been studying. Instead, it tries to measure learning with grades, and then tries to see if grades correlate with achievements later in life.
But individual students do, to some extent, have access to this privileged information about how they're studying and what they know. They might deceive themselves in any number of ways. But I would expect that most students have ways of assessing their own progress in learning, and beliefs about how accurate and useful their self-assessments are.
For example, students know the extracurricular articles they've read, and the conversations and projects they've participated in. Students can introspect about their own mind, and reflect on the study activities they've undertaken, like flashcard review, taking notes, or reading. Students have a level of self-awareness about their confidence level and raw ability in solving novel problems.
Do you have any non-obvious ways of measuring your own progress in learning? How much faith do you have in your own self-assessment? When you're reading and studying, how much do you think of the activity as "building a new skill," and how much of it is a transient test or a challenge, like a game?