Fewer high school diplomas would mean companies could better differentiate between the people who actually learned stuff and those who didn't without the former having to waste money to prove it in college.
I’m a bit confused by this comment. Are there really that many jobs that need a high school diploma (need, not require)? And I think that the second half of your comment demonstrates a misunderstanding of the purpose of college. Even if we stopped giving high school diplomas to people who don’t deserve them, people would still need college degrees for those jobs.
But regardless, if they’re struggling to graduate high school, it’s already too late for them anyway. Elementary school is where the majority of the development happens.
The damage is already done. The reform needs to happen at the pre-K-to-3rd level. Functional illiteracy is on the rise.