The school started as a junior school but quickly grew. In 1956 a senior wing was added. More classrooms and an assembly hall/gymnasium followed in 1963.
The Art block was opened in 1968 and another block – now the Junior Block – was opened in 1980.
Challoner became co-educational in the Junior School in 1992, later extending into the Senior School. At the same time, a Nursery was opened.