@temp_acc hi! I'll give you a list of non-fiction books that relate to the colonialism/history side of it:
Telling The Truth About Aboriginal History by Bain Attwood
King Leopold's Ghost by Adam Hochschild
Bury My Heart At Wounded Knee by Dee Brown
Histories of the Hanged by David Andersen
Britain's Gulag by Caroline Elkins
Unthinking Eurocentrism by Ella Shohat and Robert Stam
Struggle Without End by Ranginui Walker
Exterminate All The Brutes by Sven Lindqvist
Most of these are fairly straightforward to read and should be okay for the older students in your group. Unthinking Eurocentrism gets a bit theoretical in places, but I think it's worth a try because it talks about how white westerners view everyone else from their own perspective. Hit me up if you want fiction recs.