Arellano University - Mandaluyong Campus
Plaridel High School was first organized in January 1949 by Arellano University authorities upon the request of students enrolled at Juan Sumulong High School but residents of Mandaluyong. It was named after the great writer, soldier and nationalist, Marcelo H. del Pilar and his Propaganda movement.
The school had a very humble beginning. It was first housed in the ground floor of Flor-Premar Building on Jocson St. Mandaluyong with no less than 76 students and 5 teachers.