The school opened in September 1971 and was originally called Unsworth Comprehensive School. Its initial enrollment was 146 pupils. In 1983, the school merged with Whitefield High School (aka Albert Road) and was renamed Castlebrook High School.
Throughout 2006, along with several other schools in the wider Bury borough, it had been under a sustained threat of closure. It was believed that there will be 2,000 fewer high school pupils in Bury, so Bury Council wanted to close two high schools in the area. It was possible that Castlebrook would be amalgamated with nearby Philips High School, or that either Castlebrook or Philips will be closed.[4]
The school's GCSE results improved greatly over the next few years; with 61% of pupils achieving 5 A*-Cs in 2008, up to 76% in 2009 and to 80% in 2010, the highest the school has ever achieved.[5] However, in 2016, the school was deemed inadequate by Ofsted (The number of pupils attaining 5 GCSEs (including English and Maths) at grade A*-C in 2014 was below the national average.[6]
