It’s rather hard to get hired in a spot over GS 11/12. It happens but it’s not common. From 13 on I believe promotions are in front of a panel. Getting hired as a 15 would usually imply the hire-e was recruited.
I meant that a motivated and skilled person who enters federal service at the age of 22 in a 7/9/11 position could probably be GS 15 in their late 20s in tech in the DC area.
You’re absolutely right that getting directly hired into a higher level is much tougher, although not impossible if you are connected.
14s and 15s are relatively easy to access in a few fields in the DC area at a young age (tech and contracting are the two fields I know people who have fast-tracked in the GS system in DC). Anywhere else… not so much. Those are usually mid-career or late-career positions outside of DC area.