Some school districts do adopt informal tracking (college track, vocational track, normal track) but this is very much at the discretion of the local school district.
IB is occasionally included at local public schools in the US to help drive up rankings because College Board AP classes would require more staffing (3-4 AP physics classes can be clubbed into a single 2 year IB Physics track, and AP Stats/Calc AB/Calc BC can be clubbed into a single 2 year IB SL/HL track. In essence, you can hire 2 teachers with a Masters Degree instead of 4-5 for AP classes just in Physics and Math alone).
> I did not however go to masters or PhD programs. From my friends I understand that's where things finally get interesting
The classes that are 400 levels in a Bachelors program in North America should be comparable to those taught in the first year of a Masters program. Depending on how many credits you came into college with, you may have never had enough free slots open to take those interesting classes.