Amador Valley High School was on lockdown for about 45 minutes Monday morning as police responded to a weapon threat, according to the Pleasanton Unified School District.
District spokeswoman Myla Grasso said administrators received a report from students who heard a rumor about a possible weapon on campus and called for a lockdown at 10 a.m.
Police searched the school and found no credible evidence to support the rumor, which is reportedly now being considered a joke from identified students. The lockdown was called off at 10:45 a.m.
In the media alert, Grasso said the district considers safety a priority and that "campus administration takes all such reports very seriously."