Mercedes Schneider reports the latest twist in the evolving drama in New York state’s education scene, where Campbell Brown is trying to push erratic parent activist Mona Davids off the stage. Davids was quick to file a lawsuit and thought that Brown and Students Matter would support her, but they pulled the plug and told her to go away. Davids has been pro-union and anti-union. She was featured in “The inconvenient Truth About Waiting for Superman.” And, as we say in Texas, she has become a burr under Campbell Brown’s saddle. And Brown wants Mona to go away.