San Guillermo National High School known as Sta. Fe Extension High School was founded in June 1988 by Mayor Romeo Corpuz and his Sangguniang Bayan Member through Res. No. 101. It was approved by the Secretary of Education Lourdes Quimsubing.

In it’s 33 years of existence , the school have been managed by 13 Principals, initially managed by the District Supervisor Sir David Dumlao , followed by Madame Socorro Soria, who managed the school for more than 10 years. Madame Elizabeth Perfecto managed the school with flying colors because through her efficient and productive management San Guillermo National High School has been placed in the map of Region 3 and even in National level. After her term, the school was ruled by Sir Alvaro C. Lacuesta for ten years, shortly managed by Madame Edna Mauricio, the other Principals who managed the school were Madame Teresita Valdez, Liberty Abdon, Sir Romeo Fastidio, Edwin N. Castillo , Madame Carolyn C. Fontillas as OIC, at present Dr. Joesphine L. Raguini.

The school at present has 2, 124 enrollees, with 51 Junior High School and 19 Senior High School teaching staff and 16 Non-Teaching personnel.

San Guillermo National High School is thriving to excellence despite the pandemic.