I do admit to not knowing what I am talking about so maybe there is no danger in using the graduation rate metric.
edit: This is not an entirely serious suggestion. See later comment below.
Anyway, it wasn't a completely serious suggestion. It's got some problems. Happiness is a good thing to measure, but you'd want to still do some long term tracking of other metrics. Incarceration rates, income, college graduation rates, higher degrees and certifications, etc.
edit: I make the comment about arts schools having received a degree in film and taken a haphazard path into startups and programming that ultimately worked out pretty well. I absolutely encourage people to go to school for the arts if that's what you want to be doing.
A primary goal of school is making kids smarter and ultimately a functioning adult. Including being employable.
I don't think "happiness" is the job of an educator. The parents, absolutely. The local government? Maybe.
But if "good citizen" is a desired goal, we might be able to measure that. With surveys of alumni about current events, employment rates, financial principles, etc. To measure whether well-equipped, life-long learners are produced.
But I'd rather schools stay out of holistic goals better reserved for families.
Just because the test mean drops does not mean the test is flawed. The educational inputs could simply have worsened, which is exactly what a reliable indicator should show.
Also, nobody's suggesting moving the goal posts to explain away bad outcomes. If every school suddenly loses three points on average from one year to another on what is supposed to be the same test, the only common variable there is the test itself. The test HAS to be different from year to year in order not to repeat questions, but it HAS to remain a comparable difficulty.