The Chicago Teachers Union voted on Thursday to allow its first strike in 25 years starting on September 10 in the nation’s third-largest school district if negotiators cannot reach a contract with city officials, Reuters reports. The strike would start during the second week of classes for most of the system’s more than 400,000 students. The last Chicago teachers’ strike lasted four weeks in 1987. The union representing more than 26,000 teachers and other professionals wants improved job security, a raise, a new curriculum and a nearly 20 percent increase in instructional time, following a push by Chicago Mayor Rahm Emanuel for a longer school day. Public schools CEO Jean-Claude Brizard has said that with a projected $3 billion deficit over the next three years, the school system cannot afford the raise the teachers want…