Inosloban-Marawoy Barrio High School was established in 1968 under the support of two Barangay Captains, Fidel Pernez Sr. of Inosloban and Brigido Bernardo D. Olan of Marawoy and a community resident and educator, Mr. Justino Viñas. The high school then was under the supervision of the elementary school principal in the person of Mr. Clemente Bautista. The pioneer teachers were Mr. Justino Viñas, Mr. Eduardo Burgos, Mr. Laudelino Marasigan, Ms. Thelma Villanueva, Ms. Belen Guib, Ms. Lucy Baroja, Mrs. Lourdes Marasigan, and Ms. Merlita Lina.

      At the start of the first school year, there was only small number of enrolment since education was not given importance. Time was allotted in order to recruit more students. And, it was noticeable that the students were above their school age. The first graduates were declared in 1972.

      As years passed by, school population increased as well as its faculty members. The first school head, Mrs. Lourdes Marasign was designated as Head Teacher III. In 1986 under the leadership of President Corazon Aquino, all Barangay High Schools nationwide were nationalized. All public high schools became free of tuition fee in conjunction with the constitutional mandate of free secondary education. In 1995, the first batch of Principal position was given to qualified nationalized high schools and Mrs. L. Marasigan took over the position in now Inosloban-Marawoy National High School.

      During the reign of OIC Mrs. Milagros Bautista, principal Mrs. Gloria Ramos, OIC Dr. Ernesto Badillo, numerous developments in terms of physical facilities have been noticed as the school grows older. It was also noted how the constituents trust the quality of learning that the school offers when the number of students grows bigger. 

      From 2004-2006, a change of school heads occurred, Mrs. Crispina Pesigan and Dr. Edilberto Mercado took their post for few months and by more than a year respectively. Their leadership guided the teachers to boost their confidence to work cooperatively, competently and sincerely with the parents.

      Ms. Milagros M. Saludo had transferred in this school in 2006. Under her administration, the school was moving ahead though slowly, was continuously keeping at the right track. Student development towards good performance is the most important concern; teachers’ welfare is effortly gained; school environment is on its process of improvement along with the harmonious relationship among barangay leaders, PTA officials, parents and community. Being a three-time representative of the Division of Lipa in the Regional Contest of Brigada Eskwela is undoubtedly an evidence of the fruits of hardwork exerted by both the school’s internal and external stakeholders.