Historically speaking, I suspect there's a correlation between "virtue-focused" schooling and bodies of predominantly-upper-class students who are already nearly guaranteed to get an entry-level job in a prestigious field. The study is designed to help them compete inside a more-rarefied social circle.

Meanwhile, other students were in apprenticeships or going somewhere that focused on the on the three R's of readin', ritin', and 'rithmatic.

If the amount of virtue-schooling is decreasing per-capita over time, that may just be regression to a centuries-long mean.