[lopmotr]

If the goal of school is to get kids to learn the content of the curriculum, then that's not relevant. If you want to use it to assess how fast they learn or how intelligent they are, then that would have to be explicitly included as a goal before you designed the system. Perhaps employers and universities use school grades as a proxy for intelligence because it's convenient, but it's a little indirect. It would give falsely high scores to students who have good teachers or who hire private tutors.