Because you have to go to a high school that offers special courses, you have to be willing to work much harder than the average student, and you have to know about this trick when you're like 15yo and comprehend how much $$$ and time it's going to save you in the long run.

I fortunately did take advantage of this, and so did my wife. Thought we took advantage of it so we could do cheap study abroad and not have to take any courses toward our degree plan (indeed, I actually earned a second degree in a completely unrelated field while doing my study abroad)

But to be clear, this was because I took every advanced class offered at my high school and took other courses at the local community college instead of hanging out with my friends during lunch, etc. It was a constant gaming of the system to eventually get the results I wanted.