I've heard an argument that schools are supposed to pay for themselves. The idea is that people who go to school end up in a higher tax bracket, so it's an investment, not merely public good. Similar arguments are made for parks and recreation; more open space, less noise, so less stress-induced heart attacks, which means more years being a taxpayer.

I think this is a toxic way of thinking of things, but I guess it allows even the most greedy politician to live with himself for not opposing schools.

But then you can make the same argument about transit. It facilitates people coming into the city to engage in taxable activities.

Exactly— that's a "diffuse" benefit, and indeed the same logic that most of the world also applies to healthcare, though introducing that to a US-centric discussion just muddies the waters, for obvious reasons.

In much of the world, yes, airports are supposed to pay for themselves through landing charges, retail, etc.

In many countries, airports are privately owned and operated and make a profit. The US is, perhaps, a bit unusual in that airports are owned by governments and often subsidised.

Honestly though, you see a strong movement, especially on the right, to privatize and have those perks "pay for themselves" all the time. I've been to many state parks that require an entry fee, many city parks that require a parking fee (and are impossible to get to ootherwise). School vouchers are a first step toward full privatization of schooling.

I agree with your sentiment but let's not forget that people have been trying to fence off the commons for ages now.