Until the adjustment happens, there won't be a common way because most people are still in the current inefficient mentality so you don't get scaling effects. Whatever internships friends and family can offer would probably be the best alternative.

In the future, there will probably be some standardized test you'll have to take at age 16-18 to show that you're reasonably competent and your education wasn't a sham. (The SAT tests could probably be used as they stand for this purpose.) Then, most people will go straight to unpaid or low-paid interships in the appropriate field, during which they may have to take classes to get a better theoretical background in their field (like college, but more relevant).

After a relatively short time, they will either prove their mettle and have contacts, experience, and opportunities, or realize it was a bad idea, cut their losses, and try something else. It sounds like a big downside, until you compare it to college today.