Both of my characters are dropouts

Although actually, Rincewind doesn't really get that title because he was Expelled

He was a terrible fucking student to begin with, but then on a drunken bet he snuck into the most guarded room in the University and opened the most magical book in existence

and one of the Eight Great Spells of The Creator escaped into his head.

So they threw him out.

He was allowed to come back as an assistant librarian (and later bribed with a series of meaningless professorial titles) only decades later,

after pretty much all the prior administration were either killed or nearly ended the world and Rincewind cleaned up their mess.

He actually is very knowledgeable about magic though, he just can't perform any. But in general, Rincewind is more cunning and clever than "smart"

~Sam~ dropped out of high school because he was abandoned to homelessness as a teenager

He ended up coming into (see: stealing) enough money to make a professional life for himself, however, so he's never seen the need to go finish school or get a college degree.

But everything he learned after sophomore year of high school is the result of self-teaching. He's a naturally bright individual, so the gap in his formal knowledge has never become an issue for him

and he's still probably one of the more knowledgeable people in Bon Temps even without any pesky diplomas.