It was in 1901 that the Salesians started a small school for the boys of the district. This work was undertaken at the urgent request and with the full encouragement of the ecclesiastical authorities of the Diocese of Portsmouth.
As the number of boys increased and as boarding requirements became heavier, more building took place. A new dormitory was added, a small refectory and some additional classrooms. As the First World War drew near, the new wing and tower comprising dormitories, lavatories, etc., on the upper floor, and the staff refectory and up-to-date kitchens on the lower floor, were created.
In 1916 the area which is now the playground was acquired. The playing fields in Park Road were bought and were used in the War effort for the Grow More Food campaign. It was not until after 1921 that they came into full use. In 1927 property to the north of the playground was purchased.
During the war years 58 pupils fought and died for their country and many others were awarded decorations. After the War new classrooms were built on the far side of the church lawn, the offices of the Prefect of Studies were extended and the Cadet Force hut and new classrooms were built. Tennis courts, Ambulacrum (the covered way in the playground) and the area at the junction of Reading Road and Peabody Road were turned into a preparatory school.
In 1956 work began on the present Blackburn Building. It provided ten new classrooms, a new hall, gymnasium and changing rooms. In 1963 new laboratories and a lecture hall were built alongside the new school.
Salesian College finally became an independent grammar school in 1966. In 1970 the preparatory school was discontinued and three years later the Salesian Sisters left. In 1979, for the first time in its history, Salesian College had no boarders. From then on it became exclusively for day pupils.
The College has grown in numbers since 1979, moving from two form entry to its present four form entry in years 7-11. In 2007, the Sixth Form became co-educational.