In 1862, Handel Cossham, a local preacher, built the original village school, a British School, at Gillingstool, in Thornbury. Some years later, because of overcrowding, a new infant school building was added adjacent to the original school. In 1952 the school was separated into infants, juniors and seniors and the latter formed the Thornbury County Secondary school. Prior to this it was an 'all-age' school taking pupils up to age thirteen, known as Thornbury Council School.
In 1962, during the headship of Mr Cliff J. Martin, plans were drawn up for a new building to house the expanding secondary school. Building work started the following year on Park Road, the site used as the school's playing field. In 1965, the building was opened under the new name of The Castle School, which reflected the school's new position adjacent to Thornbury Castle, whilst keeping the same initials (TCS). The official opening ceremony took place in 1966, attended by the Duke of Beaufort, Chancellor at the University of Bristol at the time.
The county infant and junior schools at Gillingstool later formed the Leaze School, which is now known as Gillingstool Primary School.
The school became a comprehensive in 1972, the same year that Thornbury Grammar School moved from its site on Gloucester Road to new buildings in Alveston (also becoming a comprehensive with the new name of Marlwood School). The Castle School took over the Gloucester Road buildings which now form its Sixth Form Centre.
The Castle School is a thriving and successful school providing a high standard of education for all children within a caring learning environment. We are proud of our school, where high standards of work, behaviour and achievement are the norm.