Most of my computer friends and I were decent programmers by the time we entered college in the early 90's.
This was 10 years ago but I doubt it’s changed significantly. I think there’s also lots of people who don’t enroll because they think prior knowledge is required, which is a hard barrier to overcome.
Ironically, my second “better” Seattle-area high school had given up on programming as something to teach, I’m sure they’ve changed their tune now :).
Like most educational institutions they used June fiscal years, so they would buy technology near the end of the fiscal year with leftover money. Those computers would sit unopened in their boxes until September, unless you offered to take it home for the summer. I'd guess that I had a brand-new IBM PC (that cost 25-30% of our family income) at least half of the summers. You were kind of doing the school a favor - they didn't need to worry about storing it somewhere and you did the work to set it up and make sure it worked. And if a kid wanted to learn over summer vacation, they certainly wanted to help facilitate if they could.
Despite all that, I can remember going to the state programming contests in Indianapolis in 5th, 6th, 7th grades and being blown away by how much better than me all the other kids were.
The students who had programming experience from other than just their classes had a big advantage for systems work, compared to other students.
Though there were also a lot of students who had only undergrad programming experience, and had a lot more learning to do. Which is perfectly fine, so long as they know they have something to learn, and want to keep improving.
(The only annoying ones are those who treat professional and collaborative work like they're only trying to pass a class -- including the analog of only trying to get a homework assignment past the TA -- and think this is what everyone does. I suspect the ones I've seen would pass a leetcode CS101 interview just fine, because it's pretty similar metrics as getting into and passing CS classes.)