If what you're looking for is a brief overview of education as development vs signaling I would point here:
https://threadreaderapp.com/thread/976932046638538752.html
It's written by an education economist as a response to Bryan Caplan's recent book and I think it'll help give a basic notion of what people in the field think (and some understanding of the research.)
I also think a definition of 'invaluable' as 'unable to be valued' instead of 'infinite value' is necessary here. I see in another comment you've commented that opportunities shouldn't be locked behind golden gates. Even those of us who think education has a high value agree with that!
Furthermore the original comment mentions education and information. Surely you agree that information has value. But if I sat down and tried to read one of your amicus briefs it'd probably be difficult for me to understand and I'd almost certainly miss important details. So how do you learn to understand them? Education.
>Does it make our economy better and more competitive that we make kids endure school through Grade 12, and now are increasingly pushing them to do it through Grade 16? Or is it just a zero sum game?
I'm gonna quote from that link above.
In fact, signaling almost certainly is productive. Sure, in the simplest signaling model where there's only one job, education signaling is zero-sum (if you get ahead it's at the expense of others). But as soon as you introduce multiple, different, occupations, that changes! For a basic example of this, say you have two occupations, each with room to employ half the population, "Simple" and "Complex." In Simple, everyone produces 1. In Complex, smarties (half the pop) produce 4 and everyone else produces 0. In extreme-land where there's no signaling, people are basically assigned to jobs randomly, everyone gets paid a wage of 1, and average production is .51 + .5(.54+.50) = 1.5.
Now introduce a completely wasteful, no-HC education signal. Ed is free for smarties, but it costs 3 for everyone else because they'd have to hire tutors. Now, employers know who the smarties are, and they all get Complex jobs. Others get Simple jobs. Production is .51 + .5(4) = 3. Smarties get a wage of 4 and others get a wage of 1. Others don't bother going to school - they'd get a wage bump of 3 but they'd spend it all on school anyway, so why bother?
Here, signaling alone doubled production (this approach is generally called "matching"). There's a reason we call signaling outcomes the "second-best" outcome in game theory, and not "the really awful outcome" - because it can increase efficiency over NOT having the signal.
All of which is to say that education is some part signaling, some part development and mostly made up of parts that are impossible to distinguish between the two with current research methods. But even considering that it's still not a zero-sum game. And all of this is only considering the narrow range of economistic thinking about education, once you go from the frame of educating workers to educating citizens it gets even more important (and even more tangled.)
>The BLS chart shows correlation, not causation.
I mean this is almost philosophical but how would you ever distinguish actual causation there? I got involved in a thread here the other day about distinguishing environmental from genetic effects and the basic answer there was that researchers currently aren't able to distinguish certain effects. I suspect the answer here is similar