Los Angeles-area students headed back to class Wednesday morning, a day after an emailed threat triggered a shutdown of all public schools in the vast district.
School buses rolled and parents dropped off children at campuses in the second-largest U.S. school district.
The decision Tuesday to close the district with 640,000 students came after a school board member received an email threatening a large-scale attack.
District Superintendent Ramon Cortines said he ordered the closure as a precaution.
New York City schools received a similar threat but officials there concluded that it was a hoax.
It's extremely rare for a major U.S. city to close all its schools because of a threat, and it reflected the lingering unease in Southern California following the attack that killed 14 people at a holiday luncheon two weeks ago in San Bernardino.
"If this was not ISIS, not a terror organization, they're nonetheless watching," Rep. Adam Schiff, a California Democrat said Wednesday on MSNBC's "Meet the Press Daily." "And if they come to the conclusion that they can literally mail it in, call it in and disrupt large cities, they're going to take advantage of that."
