Well, just research about what plants and compounds are poisonous, and that sort of thing. Wikipedia would be sufficient.
I can imagine their daily schedules.
"Potions and Poisons 101"
"The Fine Art of Blackmail"
"History of Rome and Greece(from a poisoner's eye)"
"Courts of Law (and how to exploit them)"
"Fine Penmanship (and how to duplicate others')"
Et cetera, et cetera.