ISPP was started in 1989 by a group of families working for non-government organisations. 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 Programme set in place. Student numbers increased at the start of the school year to 11. The ISPP Charter was written and approved, establishing it as a parent-owned and operated non-sectarian, non-profit school.
By 1995 the full-time expatriate faculty numbered 14 and the student body 230. In February, following in-service training, the school developed an innovative approach to effectively meet the needs of the EAL learners at ISPP. A Biology laboratory was established for the secondary school along with the continued expansion of the Computer Lab and the Media Centre.
A committee of parents and teachers revised the ISPP Mission Statement to crystallize its focus as an educational institution of “academic excellence and responsible global awareness in a caring, international setting”. In November 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. As a result of the WASC visit ISPP was fully accredited in 2001.
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 applied for 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 been awarded 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 of International Schools (CIS) and WASC.
In 2009-2010, the faculty produced a comprehensive Self-Study for the joint 5-Year CIS/WASC/IB accreditation visit which took place in April 2010. ISPP was the first school in the world to pilot a joint 5-year accreditation. ISPP was also the first school to use Moodle as a collaborative tool to produce the self-study and supporting collect evidence.
All three IB Programmes were examined for authorization during this visit. ISPP was re-accredited by CIS/WASC in 2010 for five years and was re-authorized for all three IB programmes as well.
In 2010-2011, a new 5-year Strategic Plan was created at ISPP to guide its development well into the middle of this decade. The plan is reviewed and revised annually.
In 2014-2015, ISPP celebrated its 25th year anniversary. The Secondary School moved to the new purpose-built campus in August 2015.
In 2015-2016, 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.
In 2016, the school began to implement a new three-year Strategic Plan supported by its Operational Plan. The three areas of focus are Learning, Community and Environment.
In 2019, ISPP celebrated its 30th anniversary.
In 2020, in the midst of the global COVID pandemic, the ISPP Board of Trustees released its Strategic Plan 2020 - 2024, and the school began the re-accreditation and re-authorisation processes for CIS/WASC and the IB, once again receiving a strong endorsement from all three agencies for academic excellence.
In late 2024, the ISPP Board of Trustees conducted a community wide process to review and update the school’s guiding statements, resulting in a shorter mission statement and the addition of school values. And in early 2025, the next 5-year strategic plan was formally adopted.