Yes, there are lots of models. Problem often is funding. Need larger businesses to be involved to help fund. The fact that we mostly have small employers is a problem. Recent studies have shown that you can cut turnover in half with mentors and apprenticeships.
Turnover is a big cost to employers, but more for large employers than small ones.
Then they see results in that one person, don't need a study. But, this is a very slow process. The ultimate goal is workforce development. We have to focus attention on the learning that is going on in the classroom. Research shows that this can best be done by involving business in the learning process.