In 1956 the main block for the new secondary school, located on Piccadilly opposite Mornington Crescent, consisting of a hall and eight classrooms was built to solve the accommodation problem for a time.
This building later became the main block for the infant school.
However, almost immediately, the new school was unable to cope with the number of pupils and some had to be housed in the old Attap hut.
Initially there was no Grammar school at Changi and the school was bilateral. with grammar and secondary modern streams. It contained less than 200 pupils and the fortunate staff only had to attend school in the mornings.
In 1958 the RAF secondary schools in Singapore were completely reorganized with the establishment of a Grammar School at Changi. Two secondary modern schools remained at Changi and Seletar. This saw the introduction of the gharries to transport pupils to their designated schools.
Although Seletar school lost some of its members to Changi Grammar School it continued to grow in size and change in character. Afternoon school was introduced on Tuesdays and Thursdays. Strange new terms such as 'Houses' came into use with the strange names of Celts, Saxons and Normans; and the head Boy and girl were known as 'Dux'. Inter house rivalry developed in the classroom and on the sports field. Thursday afternoons were devoted to social activities such as Badminton, Swimming, Water Polo, Football, Cricket, Woodwork, Cookery, Drama, Ballroom dancing, Sailing Etc etc.
External exams were taken and in 1959 10 pupils took G.C.Es.
In 1960 the plan to build a school at Seletar to house all the RAF's secondary modern pupils in Singapore was conceived at the Air Ministry. Unfortunately this had to be shelved for financial reasons and the two secondary modern schools continued to exist and expand. Both now over 300 strong. In May 1963 the grammar school moved to it's new building at Changi and work was eventually started on the modern air conditioned main block at Seletar based on the original 1960 design to house 450 pupils.
Work was completed and in April 1964 there was a big move around in the schools at Seletar and the Changi Secondary Modern amalgamated with Seletar. Over 300 pupils and 14 Staff were transferred. The School Suddenly Doubled in size and, once again, the accommodation was inadequate and 10 Attap classrooms were still in use.
The School was officially opened by Air Marshal Wykeham on 16th October 1964
School days were now increased to a full day except for Wednesdays.