Some of my favs:

History/Archeology
Ancient Americas Archeology of native North & Central American peoples
Modern History TV
Townsends Exploring 18th century life

Zoology/Animal-stuff
Casual Geographic *
Moth Light Media
Lindsay Nikole *
Ze Frank’s True Facts This is the kid-friendly version of his channel

Astronomy/Astrophysics
Dr Becky
PBS Space Time
Both of these might be a bit above a pre-teen’s understanding. I would have loved these as a kid, complexity be damned.

General Science
PBS Nova

Earth Science
PBS Terra

Chemistry
ACS Reactions

Art & Literature
Great Art Explained
Great Books Explained

*: language/subject matter/style might not be a good fit for younger children.