Police said students on Thursday discovered the graffiti message in a bathroom stall.
School officials contacted the Central Marin Police Authority about the message.
Police said the school would maintain its usual Friday schedule.
As of Thursday night, there was no evidence to support the credibility of the threat, police said.
As a precautionary measure, the Central Marin Police Authority will have a visible presence on the campus throughout the day.
Just over a week ago, officials canceled classes for the day due to a bomb threat.
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Anyone with information related to the incident is asked to contact the Central Marin Police Authority at (415) 927-5150.