Big thing is the realization of how little time you really need to learn the material presented.
They could go with an online/homeschool/brick&mortar system and have all students, regardless of which type of study they choose, take an HS exit exam. One for basic RRR, and one for majors. That is, HS students would choose 2 major courses of study. Keep the SAT for college bound. HS majors would be good, because some schools would specialize in trades, others in STEM, other in business, etc.
I think aptitude tests for business applications should be brought back. That would cut out the unwritten college degree requirement. Save some kids big bucks.
Keep HS sports (good for the community, especially traditional rivalries), but allow online/homeschool in district/brick&mortar students. access. My experience with club sports is it becomes too expensive, and exclusive/political wrt to traveling teams, etc.