Los Angeles closes all schools after receiving threat

Los Angeles, the second largest school district in the United States, shut down all of its schools on Tuesday after officials reported receiving an unspecified threat and ordered a search of all schools. Officials asked parents to keep all of the system's 643,000 students at home to allow time for a full search of more than 1,200 schools, from primary through high schools. It was the first closure of the full district in at least a decade, officials said, and appeared to be unprecedented in scal