Another might be seeing the lack of women plumbers (or whatever) and deciding that this is both bad and fixable and investing a bunch of money into advertising how awesome plumbing is to girls in school.
I'm not sure I follow. Are you suggesting that we, as a society, should not invest in worst performers? How would we even know beforehand? And how would withdrawing such funding from "bad" schools not affect the opportunity of all of the children of that school?
What's your point about the gender ratios of certain occupations? That it's a waste of money to try to alter?
I don't have the time to give an in depth discussion on education etc the attention it would need.
Though to elaborate on the education policy difference, you can invest variable amounts into the bottom performers, even eventually giving up on them. As I understand it, schools currently have various legal obligations towards students that lead to them spending disproportionate resources on the least performant.
What would be the difference in public policy anyways if after-the-fact results differ?