I am curious about this too. It appears that in our school district, a standard course load will be 6 units, a rigorous course load will be 8 -9 units (see example below). Taking 9 units will involve skipping lunch which I have heard some high school kids do. Caveat: my kids are not in high school yet, so I am not speaking from actual experience. Perhaps people with more experience can post a typical course load for junior and senior load for a strong student in their school.

The science course in my "rigorous course load" example refers to regular or honors science. AP science as I understand it will take up 2 units (1 unit for the regular class, 1 unit for lab).

English (1 unit)
History (1 unit)
Science (1.5 units)
Math (1 unit)
Foreign Language (1 unit)
PE (.5 unit)
Elective (1 unit)
Elective (1 unit)