Vanden High School is in the Travis Unified School District. No other schools are affected.
Officials said they were made aware of the threat yesterday and closed the school as a precaution.
Earlier this month, offensive graffiti was found on campus. The school isn't saying if this threat is related.
The family of a student held a news conference with NAACP leaders in San Francisco today. They say the graffiti included racist comments about their son, and that today's closure is because of a separate, racist threat.