It opened in 1990 at a leased residential villa at Way 317 of Wuttayah Street in the Al Wattayah district with 38 students handled by volunteer teachers, before the arrival of the hired principal, Elenita Fernandez, in June of that year.

After producing its first graduates in the form of preparatory pupils, followed by the arrival of the first preschool teacher Mrs. Rosario Ballesteros in September 1991, the school was recognized as a learning institution by the then Ministry of Education and Youth.

With the residential area of al-Khuwair deemed unsafe for the growing student population, the school relocated to al-Farahidi street in the district of Ruwi, where it would be based from 1993 until 1995.

It has been operating in accordance with the laws of the Republic of the Philippines, particularly along organization, administration, and supervision for private educational institution; likewise, with the Sultanate's Ministerial Decree No.

By early 1995, in response to the rising number of students living in faraway districts, the school's Parents-Teachers Association lobbied for a site located at the center of both the city and the Muscat Governorate.

With the government granting this request, a spacious building at al-Inshirah Street in Madinat Qaboos became the school's next home from 1995 until 1997, along with the hiring of new teachers.

An additional four new teachers joined the teaching force for the year 1996-1997 in order to handle the growing student population.

With a decision to permanently settle in the Al-Khuwair district made in 1999, the continued increase in the student population necessitated the opening of an annex campus at Way 4144 of al-Kuleiah Street in the year 2000, where two departments: preschool and the first two grades of elementary primary level (Grades 1-2), were moved to and based in until 2001.

Since then, the school had evolved from a simple academic institution into a highly-structured organization, growing in terms of enrollment and size.

PSSO used the 1945-2017 basic education curriculum from 1990 until 2015, which consisted of levels from kindergarten to fourth year high school.

Since the school year 2004-2005, English has been the subject's medium of instruction in order to accommodate foreign students and to help enforce a proper English-speaking policy.