Goodhart's Law (that quote) is actually one of the motivations for moving away from ACT and SAT as college entry benchmarks. "Teaching to the test" is a rampant problem in the US.

UC is seeing flaws in departing from those benchmarks, though. The thing is, % of students getting admitted to college is itself a measure for schools and school districts. If GPA is how you get kids into college, well...

It's not a teacher problem, it's a district and state problem. As a teacher, if kids are failing your classes (which nowadays seems to be "getting anything less than an A") your school district blames you.

To me, it seems that Goodhart's Law is an inherent problem for education in the information era, no matter how you cut it. If there's one good thing that can be said about ACT and SAT, they're relatively difficult for schools to game. GPA inflation is trivial.