A (disciplined) 6th grader could probably balance 2 AP courses in their schedules
because
the AP classes aren't that difficult but its rather the Honors classes that are
Ironic, isn't it?
It's probably because of the massive workload that my English teacher assigns the class every week (we need to read a new chapter on The Lord of the Flies and write multiple paragraph-type responses for specific sections of the chapter/book)
There's also math too, im kinda lacking in that department
But anyhow the AP classes dont assign too much homework (partially because its literally the beginning of the school year)
Like my Biology teacher doesn't assign (relatively) intense homeworks and my World Hist hw is somewhere along 25-30 pages of notes within a short window of time (as in 1-2 days) every once in a blue moon, and its sorta manageable cuz its only notes and not annotations (disgusting)
I guess studying for the AP tests is very important and specific but what else could you expect from a "college-level" test
These aren't even college level courses, my older cousin (he goes to Pitt) literally showed me his Biology class notes and they're at least 25X harder and more specific in comparison to the stuff that I learn
but we do go at nearly the same pace as colleges so that's pretty fun
ok I'll stop ranting now

TL, DR: AP level classes aren't as difficult as Honors level classes.
adios