> if pedagogical methods are getting better over time, th
This is a faulty premise from the get-go. Human learning, and teaching, go back hundreds of thousands of years. It goes back farther than any technological invention, before the knot, before fire (hell, we wouldn't have those but for teaching/learning). We've been doing this a long fucking time. If we weren't good at it, we wouldn't be the technological (or artistic, or philosophic, etc) species that we are.
We've gotten pretty close to optimal, and we did that centuries or even millennia ago. We're definitely in an era of diminishing returns in pedagogical research. And if we could be honest, this certainly isn't a hard science. Hell, it's usually in the college of education, and not included in the college of social sciences. If we could believe that it was less of a pseudoscience than, I dunno, astrology, then I might even think that there'd be this principle of "we teach to maximize everyone's potential" and not "if done correctly, identical outcomes are possible for every individual". So, no, I have no evidence to support the idea that people who would've flunked 50 years before could magically be made to pass today with the same material.
> On the other hand, grade inflation makes it harder to filter above-average students from below-average students.
This is in part because the grade no longer signifies a measure of knowledge of the materials, and is rather a rubberstamp. But it is also the case that in coddling those who did not deserve to pass, there was no longer enough resources to properly teach those who might've genuinely earned a passing grade in the previous era. This is hidden anyway due to the grade inflation.
>You could combat this by grading on a curve or by making exams harder, but this risks driving students into deleterious zero-sum behaviors - see Asian "cram schools" or American "tiger parenting".
This is plainly false. If people come to understand that you can't cheat or force the grade through Asian tiger parenting, then everyone understands it's just pointless to try. And we return to uninflated grades. But that's a little too unprogressive, I think, for us to ever return to that outlook.
Grade inflation is the proof everyone uses to justify to themselves efforts towards cheating grades. "See, dumb people can get good ones too if they just figure out the correct hustle!" Some of these are more admirable than others ("I'll just study 39 hours per day!"), but it amounts to the same. People who will never understand the material believing that this is not a fundamental barrier to success in that field cause all sorts of problems.
> On the gripping hand, maybe grades are the wrong thing to focus on.
If we do away with grading, how is that any different than giving everyone an A/4.0/whatever? Except, maybe it's a little less work for the instructor who no longer has to scribble down a letter next to each name?