I think Squeaky Fromme and John Hinkley are on a par famousity-wise (while Reagan and Ford are not).
I learned about neither in a class but, probably, from PBS. Public school history for me never even made it to World War I chronologically.
But PBS, ah PBS. They air shows on presidents, on the Manson Family, on nuts who try to kill people. And they taught me to respect other people's imaginary wooly mammoths and how to paint happy trees.

(Oh, and Carter is the shit! Just like PBS.)