>I dunno, maybe it differs by country/location but my perception is that school was never capable to educate beyond some basic mediocrity level.

You just need to look at educational league tables between countries to see there is a spectrum of results and some places are much better than others.

Personally I think the problems are rooted in inequality. If the elite all send their children to private schools then why would they care about the poor state of public schools. The country that regularly comes out at the top of the league table for educational attainment has almost no private schools.