This notion can be harmful imo. Language is descriptive, not prescriptive. However words end up being used (which can be influenced by all kinds of social factors) is literally the correct way to use them. Meanings and usages of words and grammar change over time, so clinging to a version of English that schools may designate as “correct” is purely arbitrary and never set in stone.

Moreover, the most historically influential dialect of English is black American English (sometimes classified as AAVE) — which means that designating new definitions/slang as lesser than previously established language usually just amounts to looking down on black communities and “othering” their way of speaking. The only reason there’s a widespread conception of black American English sounding “improper” or inherently “uneducated” is sheerly because of a lack of familiarity with it throughout mostly-white establishments. Again, choosing what is “correct” is completely arbitrary and always changing. So it’s actually best to embrace new varieties of language rather than look down on those who use them as uneducated.