[raarts]

> Like most developed countries, absolute scores have slowly decreased over time. It's not clear why this is happening.

I teach in college. I was born early sixties. My daughter teaches math in high school. Recently I showed her my math books from my old high school. Her response: No way that my students could follow this.

Where I teach we have to give extra classes in basic math (I'm in STEM).

We're definitely sliding. Reading seems to be sliding worse even.

By the way, I don't think there is much of a correlation between how much a country spends on education and the quality of it.