> That can't possibly be true

It tracks with spatial inequality.

A 1 school town is highly likely to be a small rural town with limited economic prospects. Like plenty of CEE countries, the overwhelming majority of opportunities have historically been clustered in the capital and a couple regional cities.

The kind of town or village with only a single school is going to have fewer social benefits or services compared to an urban school.

Basically, what it is saying is students in those kinds of towns are s** out of luck statistically speaking compared to their urban peers.

There's a reason Romania's HDI has remained lower than Russia's until recently thanks to EU funding to help develop Romania (which is now on track to become a major economic pole in the CEE)

Edit: can't reply

> A lot turns on this. (I suppose I could read the underlying paper, but I'm lazy.)

I recommend checking it out. It explains the methodology and some potential wonkiness. It's always good to read the docs

I acknowledge that effect is present, but it's simply not strong enough to dominate natural variation in ability (for which high school entrance exam scores are a proxy) to the point where the results are completely flat -- in fact, students who achieved the highest scores on the entrance exam were slightly lower in exit scores on average than those with low or medium entrance scores!

What this tells me is that some kind of correction is being applied to those y values (we already know this because of negatives numbers on a "percentile" axis) -- but what?

A lot turns on this. (I suppose I could read the underlying paper, but I'm lazy.)