The title says it all. The most current estimates hover around 30% nationwide. Dual enrollment refers to any instance of high school students taking coursework that is college-credit equivalent. This is usually AP classes or arrangements with local colleges to offer college coursework to high school students (either at the local high schools or via online access or via special access to local colleges).
The average amount of credit completed varies by state from a semester to around a year of college. This means, of course, that a substantial fraction of high schoolers are normalizing taking up to a year’s worth of college classes while being under age 18. Kind of puts a lot of claims about what a college degree measures into different perspective. In some parts of the country, most students are taking a year of college coursework in high school.
The steady rise in dual enrollment is related to my previous post about the increase in youthful PhDs. There is a growing pool of students who are responding to credential pressure by simply starting much earlier in the process. The interesting question is how far we are from the tipping point of something like 1/5 or even 1/3 of college students getting BAs before 20. It’s hard to say.