UPDATE 1-Los Angeles teachers begin strike, 640,000-student school system shuts

More than 30,000 Los Angeles teachers demanding higher pay walked off the job in the second-largest U.S. school system on Monday, leaving hundreds of thousands of students in limbo, union officials said.

About 640,000 students arriving on Monday for classes at some 900 campuses in the Los Angeles County School District were met by teachers carrying picket signs and rallying in the rain for higher salaries, increased staff and smaller classes. (Reporting by Dan Whitcomb in Los Angeles, additional reporting by Rich McKay in Atlanta and Gina Cherelus in New York; Editing by Ed Osmond and Bill Berkrot)