What is school for? We could dive into the history of public (and private) education since the industrial revolution and analyze policy decisions by state legislatures to get an answer to this question, but that varies heavily from state to state, school to school, and era to era. More simply, let's observe and figure out from our own experiences what school is really for: compliance, or education?
An example: Which draws more attention, a kid who learned absolutely nothing but has passed every test due to their memory (passed compliance test, but didn't learn), or the kid who has failed every test because he desperately needs context in order to remember the information (didn't pass compliance test, didn't learn)? The latter who didn't comply.
Another: Which is more concerning to a teacher, a shy, quiet kid with failing grades (complies behaviorally, fails academically) or a loud, outgoing kid with failing grades (doesn't comply behaviorally, fails academically)? Again, the latter student who fails to comply, despite the fact that both are not learning.
School is not for education as it currently stands. Usually has very little to do with real learning going on in the classroom, but making students comply. In both of these above cases, the educational component is lacking entirely, but that's not the primary concern. The primary concern is that the student be processed correctly.
A Manufacturing Process
Let's compare two factories:
The first factory produces a car, specifically a midsize sedan with 4 doors that only comes in one color. Every tool in the entire factory is made to produce specifically this one make and model, from door to dashboard. The vehicle only comes in one color because it would be much more expensive to offer multiple paint options. Sometimes defective parts are produced: quality control finds them and then they are simply thrown away. This factory produces cars in large batches, and it's goal is to produce as many cars as possible in a given year (measuring success with vanity metrics).
The second factory is less of a factory and more of a custom shop. This shop meets and works for all sorts of car owners that want an awesome car built. Each and every owner brings the shop a project with unique problems, features, characteristics, and goals. There is no standardized process, because it would be impossible to throw all of the projects into one process under the assumption that they should all meet the same standard. This shop, since it pays so much attention to each individual car, produces cars in small batches, and it's goal is to produce the best, highest quality cars that it possibly can, regardless of the number produced.
Which sounds more like the schools you've attended?
Scarily similar to a manufacturing plant, schools are large organized institutions meant to process as many kids as possible in the most efficient manner possible. It reduces people to mere numbers in a grade book and in an annual report on "academic readiness." Whether or not the institution intends to do so is irrelevant: every student that's ever spent time in the average public school knows exactly how it feels to go through standardized processes and procedures that feel like human quality control. Just like a manufacturing plant, if each product can be made to the exact same specification, then the process can be repeated to produce a large number of students each year.
What if the school system looked a little more like a custom shop? Each and every student would walk in the door to develop a relationship and become a better individual through real education. Time would be taken to establish context with the students and diagnose problems before prescribing a solution, not the other way around. There would be no standardized process or mold to fit each of the students into. Success wouldn't be measured by mere numbers anymore, but on validated learning and later career success. Kids would leave the institution not only with information but unique knowledge sets and problem solving ability. They would not only learn, but learn how and why to learn, practicing the art of self-education, not just compliance.
Unfortunately, that would take a lot more effort. It's not efficient, it's not easy per se, and it sure as hell isn't happening currently. It's still the right thing to do.
At the end of the day, what does a diploma represent? Considering how remarkably easy it is to graduate high school in the United States, does a diploma represent a distinguished level of education? Intelligence? Creativity? Or just compliance?