I work with rural schools in Mexico which employ an interesting model. Because the communities are too small to qualify for a regular school they are sent education student who teach in the community in order to earn a free or half price college education. One year of teaching = half price, 2 years, full funding. These young teachers receive training and are supported by a network of master teachers. There’s also something similar for doctors who have completed their training.
While I don’t think this precise model could be used in the US I like the idea of an expanded Americorps-style service program post-high school. There are lots of areas where we could use healthy 18 year olds- the military, public works projects, as school aides, in disaster relief, and so on. Plus it would give kids a year or two to mature before proceeding to college.