Let’s say we are trying to get across the language situation in Norway where at least 2 forms of language compete. We show two different plural formers: boeker and boka and say both are acceptable but belong to two different standards.
Students may ask, do we have anything like that in English? Most instructors would jump to the very minor differences between American and U.K. English in spelling (labor~labour) or vocabulary (hood~bonnet). But those are not grammatical differences. What is an example of a grammatical difference?
Well, clearly, we could cite he saw~he seen or you went ~ you all went or he doesn’t have it ~ he don’t have it or he might be able to go ~ he might could go or there isn’t ~ there ain’t or we don’t have any ~ we don’t have none. Most of the variants could be ascribed to a sort of general Southern English of Scots-Irish origin but generally Southern though many of these usages extend far beyond the South.
The problem is the students will react with “But that’s bad English!” They have been so brainwashed by the idea that simple variety is somehow dangerous and undermining of the faithful that they simply cannot be brought to see/hear these without concurrently passing on an air of stupidity and backwardness, inculcated by generations of school marms.