In 1911 when this school was registered as an assisted school there were 325 students on roll. The first principal was Thomas E. Gunarathne.

The land for the school was donated by the Rankoth Viharaya while the buildings were constructed out of public funds. The school was managed by a Board of Management and funds for the running of the school were met by philanthropists and the general public.

Due to the rapid expansion of the college the Rankoth Viharaya premises became congested and there was the necessity to re-locate the college. The manager of the Board of Management tried to relocate to Walawa Waththa in 1942, where Sri Sumangala College is presently located. When this failed, the management decided to shift the college to Nalluruwa. The first old boy of the college, Walter Salgado, donated the land for the main buildings and M. C. Fernando donated about 1.0 ha (2.5 acres) to be used as the playground of the college.

The main hall of the building complex was donated by Leo Fernando; physics, chemistry and biology laboratories were donated by P. C. H. Dias and the main building and the class rooms were built with public donations.

All the classes from grade six upwards were taken to Nalluruwa new buildings on 7 August 1942. Grades 3,4 and 5 were continued at the Rankoth Viharaya premises and it was popularly called town branch of the college. The principal or the head of this section was A. C. Morawaka who served the college until his retirement.

With the transfer of the college to Nalluruwa it became one of the leading educational institutions where laboratory facilities were available for the students to do science subjects in the medium of English. Advance level students of the Sri Sumangala Girls School used the laboratories in the afternoons to do their practicals. The plot of land between the main college and the play ground was eventually acquired by the Education Department.

In 1961 a large number of schools were taken over by the government and the town branch was registered as a separate school with a principal being appointed by the Education Department. A precedent was created to admit all the children who leave town branch after they passed the grade five test. In 1992 due to inclement weather the retaining wall of the Rankoth Viharaya collapsed damaging the main hall of the town branch. The school had to be kept closed for a few months. The Old Boys Association, parents and well wishers constructed 18 semi-permanent class rooms and the Town Branch was amalgamated to the main college.

On 25 May 1993 the College was declared a National School by the Ministry of Education.

Devastated with the Tsunami struck in 26th December 2004 and with the blessings of the Government of Sri Lanka, Mr. L.W. Somatilaka – Principal, OBA, Teachers & staff, Students, parents and well wishers, the uphill task of the initial works related to the construction of a brand new school was commenced amidst challenges, logistical problems and obstacles at a land belonged to CTB & Army with an extent of approx. 7+ acres in close proximity to Panadura Town along the Panadura – Horna main road with the grant funding of Government of Japan. The Japan International Corporation System (JICS) who executed the construction work and the contract was awarded to by end October 2005 to Buildmart Co. The consultants to the project are Mhori Architect & Associates Inc, Japan in association of Surath Wickremasingha Associates, Sri Lanka.

As a result the construction of the proposed new school could only be commenced with a foundation laying ceremony on 6th July 2006. The total cost estimate (including consulting,construction supervision etc.) of the proposed project is Rs. 390 million (approx. USD 3.3 million). The new school will have many new features, added and enhanced facilities such as new main Auditorium, A spacious Library, Computerlaboratories, Auditorium for the primary school etc. for the use of students. Having successfully overcoming the obstructions, finally all the proposed works under the project was completed by end March 2009.

His Excellency the President of Democratic Socialist Republic of Sri Lanka Hon. Mahinda Rajapaksha ceremonially opened the newly constructed complete school funded by the Government of Japan on 23rd April 2009 at 1630Hrs with the participation of His Excellency the Ambassador for Japan Kunio Takahashi, Minister of EducationHon. Susil Premjayantha, Deputy Minister Postal Services Hon. M. Sellasamy, Minister of Nation Building Hon. Rohitha Abeygunawardena, Former Chief Minister of Western Province Reginold Cooray, Mr. Lalith Weeratunga Secretary to HE the President, Director Media of HE the President Mr. MahindaIlleperuma, Mr. Nimal Bandara, Secretary, Ministry of Education, Inspector General of Police Jayantha Wickremaratne and MPs, Senior Government Officials and other distinguish guests. To mark the Centenary of the school a commemorative Stamp & first day cover was also issued on the same day.