What happens when you give a microphone to a public school teacher?     That’s not a rhetorical question. I really want to know, because we so rarely let educators speak in any context other than the classroom.     Maybe that’s why it’s so refreshing that MSNBC is hosting “Public Education Forum 2020: Equity and Justice for All”on Saturday, Dec. 14, in my hometown of Pittsburgh.     Public policy is usually made by billionaires who…