The public schools are these kids' last and only hope to learn the communications skills (aka standard English) they will need to make it to the middle class. Don't ruin it for them.
She says that these kids are speaking AAVE because that’s what they know; it’s not wrong — it’s their language. She thus advocates teaching students who speak AAVE at home the concept of code-switching. The general idea is simply the notion of switching between two different languages as needed.
No one is advocating that students aren't taught formal English, but that the language they speak is properly recognised. Doing this will actually improve students' ability to learn formal English.