ISPP was started in 1989 by a group of families working for non-government organizations. The first six students, aged three to seven, met part-time in the home of one of the parents who was also the teacher.
In 1990, in a rented villa, ISPP took the first real steps to become a normal day school. A curriculum was developed and a kindergarten to Grade 4 programmme set in place. Student numbers increased at the start of the school year to 11. ISPP's charter was written and approved, establishing it as a parent-owned and operated non-sectarian, non-profit school.
A committee of parents and teachers revised the ISPP Philosophy-Mission Statement to crystallize its focus as an educational institution of "academic excellence and responsible global awareness in a caring, international setting". Following that, a preliminary candidacy visiting team from the Western Association of Schools and Colleges (WASC) visited ISPP. The visiting team members examined many of the school's documents including its curriculum, policy manual, charter, financial reports, and Philosophy-Mission Statement and spent many hours in classrooms.
Early in 1996, a formal learning support programme was developed and a full-time learning support teacher was employed later in the year. A strategic plan was also developed for the integration of technology into the ISPP curriculum. A technology committee was established to facilitate this plan.
In 1998-1999 the school presented for its final international accreditation with WASC following three years' provisional accreditation. The full accreditation visit took place in March 1999 and in May the school was notified that it had scored a full 6-year accreditation at its first attempt! Success meant that ISPP became the only fully internationally accredited school in Cambodia at that time.
1999-2000 saw a number of other significant developments take place. A decision had been made by the Board to become an IB World School. The International Baccalaureate Organization (IB) carried out an authorization visit and approved the school as an IB Diploma school.
In 2001 the school was also authorized to offer the Middle Years Programme (MYP) of the IB and the IB Primary Years Programme authorization was granted in September 2004.
During the 2004-2005 School Year, ISPP was also accredited by the Council for International Schools (CIS) and WASC.
In 2009-2010, ISPP received its 5-year re-accreditation by CIS/WASC and was re-authorized in all three IB programmes (PYP, MYP and DP).
In 2010-2011, a new 5-year Strategic Plan, which is reviewed twice a year, was created at ISPP to guide its development well into the middle of this decade.
In 2013, a visiting team for CIS WASC declared that ISPP was fully prepared to begin an 18-month self-study that will culminate with a 3 agency visit from CIS/WASC/IB in 2015.
In 2014-15, ISPP celebrated its 25th year anniversary. The Secondary School moved to the new purpose-built campus in August 2015.
In 2015-16, the Early Years Centre and the Elementary School vacated the last two campuses in BKK1 and joined the Secondary School on the new campus. In November 2015, ISPP received extremely positive reports from its accreditation and authorisation bodies CIS/WASC and IB and gained full re-accreditation for the school.