During WWII, the Nanyang campus was used by the Japanese soldiers as a military hospital. When the Japanese surrendered in 1945, British soldiers returned to Singapore. On 1 December 1945, the British military government gave the school permission to occupy the former Japanese Association premises, which later became the office of Chinese Christian Youth Association, at Selegie Road.
In January 1947, the British army informed Nanyang that the Selegie Road premises were to be used for other purposes and asked that the school move back to the King's Road campus. In 1948, the Board of Directors bought the land on a hill behind the King’s Road campus for $10,000 and built 4 classrooms to serve as the primary school section.
As the school continued to grow, a new Administration Block, a Hall Block and Science Blocks were added.