Student or Learner
‘He’s had things too easy for him. I’ve been much too indulgent. There’s never been a thing he wanted that I haven’t given him. I’ll learn him.’
(W.S. Maugham; The Alien Corn)
Would everyone understand me right if I said, for example: "I used to learn universal grammar when I was a Visiting Professor of Linguistics at Oxford University"?learn
now chiefly substandard : teach
Webster's Third New International Dictionary of the English Language
(I've got some doubts that I could ever say so, though...)
As Rover says, it is grammatically correct and should NEVER be used in formal English.
I think "I'll learn you him/her/them" actually almost exists as a phrase in and of itself, as a threat with the meaning that you plan to administer physical violence of some kind, as a punishment or to teach someone a lesson. Would that meaning fit your context? You can see it here on Urban Dictionary (meaning 4) which isn't the most reliable source I know, but it's definitely something I hear used in BrE. The usage of it with that meaning is still thought of as ignorant and uneducated and should be avoided in your own speech but would be fine if you were doing a piece of creative writing where your character was supposed to possess those qualities.
Boy is that an understatement! I really want to weigh in and say that if you used "learn" in this way, you'd be laughed at. To me, teach and learn are verb pairs*, and mixing this one up sounds especially uneducated. (*I think there is a more formal description for verbs like give/take, come/go, loan/borrow.)
I myself would use it most sparingly, and usually only in this form:
Friend: My son loves to ride down the street on his bike with no hands! He just crashed and broke his arm.
Me: Well, that'll learn him.