That's interesting because in the 1960 novel To Kill a Mockingbird (widely taught in the US and well-known in other countries), there's a scene where the character Scout is criticized in school by her teacher, when it's discovered that Scout learned to read ahead of the curriculum, from her father at home. The teacher expressed the concern that Scout might end up learning how to read incorrectly. If I remember correctly, the end result was that Atticus (Scout's father) told his daughter that she could secretly continue to read at home, just without telling her teacher, to avoid conflicts in class.
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Except from the novel (where "I" is the character Scout):
“Teach me?” I said in surprise. “He hasn’t taught me anything, Miss Caroline. Atticus ain’t got time to teach me anything,” I added, when Miss Caroline smiled and shook her head. “Why, he’s so tired at night he just sits in the livingroom and reads.”
“If he didn’t teach you, who did?” Miss Caroline asked good-naturedly. “Somebody did. You weren’t born reading The Mobile Register.”
“Jem says I was. He read in a book where I was a Bullfinch instead of a Finch. Jem says my name’s really Jean Louise Bullfinch, that I got swapped when I was born and I’m really a-”
Miss Caroline apparently thought I was lying. “Let’s not let our imaginations run away with us, dear,” she said. “Now you tell your father not to teach you any more. It’s best to begin reading with a fresh mind. You tell him I’ll take over from here and try to undo the damage-”
“Ma’am?”
“Your father does not know how to teach. You can have a seat now.”
I mumbled that I was sorry and retired meditating upon my crime. [...] I knew I had annoyed Miss Caroline, so I let well enough alone and stared out the window until recess when Jem [Scout's older brother] cut me from the covey of first-graders in the schoolyard. He asked how I was getting along. I told him.
“If I didn’t have to stay I’d leave. Jem, that damn lady says Atticus’s been teaching me to read and for him to stop it-”
“Don’t worry, Scout,” Jem comforted me. “Our teacher says Miss Caroline’s introducing a new way of teaching. She learned about it in college. It’ll be in all the grades soon. You don’t have to learn much out of books that way—it’s like if you wanta learn about cows, you go milk one, see?”
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Contrary to this approach in teaching, in my university courses, my professors in math and the Spanish language always encouraged additional reading and study outside of class (oftentimes, this was written directly in the syllabus or part of class discussions). So, I haven't heard much about professors being concerned about students learning the "wrong way"—I suspect that many educators are happy in general when students seek to learn from additional materials outside of what's presented in class.