Anonymous wrote:My children hear Standard American English at home, spoken in a Standard American English accent. When they go out into the world, they hear different versions of English, spoken in different accents. Nothing bad has happened yet.
This. The parents' influence is greatest.
OP, my son goes to a little private school out in the burbs. His teacher is very smart and talented. Love her. But she's from rural Pennsylvania and still speaks like it. Which includes things like "could have went." Nails on the chalkboard for me. But my son doesn't pick it up. I'd take a little more caution with the choice of books you read to him in the early years. Pick ones with good grammar.