There are roughly two methods of science, I hope we all agree in that. One is the empirical and the other is the theoretical (axiomatic in my book) method. In schools they don't have the time or tools or whatever to teach these two properly. So either there are (I wouldn't say flaws but) big jumps and lots of unproven statements in theoretical sciences and a ton of empirically unproven statements. So the system doesn't measure how well you do science but can you be a well-functioning member of society. Without basically any useful knowledge about the driving forces of society or morality. And when society is fucked up this can be a very dangerous thing.

And I think that is similar to Lock's opinion on the matter because in fact they limit the knowledge to certain categories based on how can we serve the institutions wich have heaps of money and 0 morality at all.

Edit: an example of shitty education is how they teach evolution. Since it is not based on science basically getting an A in evolution is the same as getting an A in creationism. Just learning some kind of pseudo-science. Now does getting an A in creationism mean anything? Now does getting an A in any kind of pseudo-science mean anything at all? A major part of education at any level is just pseudo-science or a practical knowledge to get a job at a profit-oriented institution. Therefore I think it is immoral to classify people based on grades in these subjects.

Generally I think we grade to show knowledge of the subject matter.
Does one know the names on the continents or countries or states and can place them on a map, etc.
Grades are not an indicator of ability, intelligence, worth, etc.
It is when we assign some value to grades other than what they really show that we get in trouble.
We grade so that we know a particular skill has been mastered and to assess readiness for additional education, that is all.

Frankly I think grades and salaries are both essential to the stability of society.
It is high differentials in salary leading to large income inequality which is a problem
It is taking grades to mean something other than ability or achievement in one area that is a problem

Well, grades are an honest assessment, unless favoritism then that's immoral. It's more about being able to follow directions and present something of substance. We get graded all the time in reality. Should we all make 100% free throws in basketball? It's okay that some people are better at something than others.

Salary is about supply and demand. If not many people are doctors and we need doctors, then they can command a higher salary. All they have to do is say find someone else if they are being low-balled. Salary is also negotiation and a mutual trade.