Schurr High School is closed and will delay the start of the school year as the district works to resolve the issue.
Interim Superintendent Mark Skvarna says they're working with experts, including an industrial hygienist.
In a note to the school community, Skvarna said the rat problem was discovered as the school was performing a maintenance assessment and an evaluation of the heating and air-conditioning system.
"Out of an abundance of caution, it was determined that the best course of action was to delay the start of school for everyone's safety," Skvarna wrote.
The district says it will provide more updates as they become available.