I dispute this assertion. When I was growing up, Ireland was ethnically homogenous with poor economic security and hostility to welfare cases like those of single mothers (for religious reasons), but there was still a distribution of ability and academic application. there were poor kids that studied hard and rich kids that didn't give a fuck, though more of the former than the latter, since high schools there employ streaming. You need more evidence for this assertion that the existence of welfare automatically results in poor academic outcomes.

I suggest that the disparity of result may have always existed, but in the past there were fewer women in the workforce and more jobs in manual labor such as manufacturing etc., so that a lack of academic achievement didn't necessarily result in economic insecurity.