From The New York Times: As parents here prepare to send their children back to school next week, the union representing Chicago Public Schools teachers gave a 10-day notice on Wednesday of its intent to strike, the next legal step in a series of maneuvers amid continuing contract bargaining with the city. “C.P.S. seems determined to have a toxic relationship with its employees,” Karen Lewis, president of the Chicago Teachers Union, said at a news conference announcing the move. “We have been belittled, bullied and betrayed by this administration.”