Schools test often to teach inequality and hierarchy
At school, our kids are rated and ranked far more often than most adults will tolerate, even though this actually slows their learning! It seems that modern schools function in part to help humans overcome their (genetically and culturally) inherited aversions to hierarchy and dominance. Modern workplaces require workers who are far more accepting than are foragers of being told what to do when, and of being explicitly ranked, and our schools prepare kids to accept this more primate-like environment.
The evidence strongly suggests that students learn better when they are not graded and certainly not when they are graded on a curve.
Subjects worked on different tasks and received performance-contingent payments that varied in amount from small to very large relative to their typical levels of pay. With some important exceptions, very high reward levels had a detrimental effect on performance.
This is Robin Hanson of Overcoming Bias making a plausible point, though I would not view this at all as a recent phenomenon. If anything, accepting hierarchy and dominance is probably less important today than it used to be at any point since pre-history.
Do click through, there's more interesting stuff there.