The accommodation in 1973 consisted of the old Ty Celyn School Llandennis Road, Cardiff, with a new building attached, designed for six form entry.

An extension was completed in December 2013 which added a multi-purpose space, Neuadd Celyn, for theatrical performances, and additional classrooms.

According to the latest inspection report by Estyn, the school is rated as Excellent and, 'the standards achieved by pupils are consistently very high and well above expectations.'

[5] Cardiff High School has been the site of filming for episodes of The Sarah Jane Adventures, a Doctor Who spin-off show during 2008 and 2010.

Episodes filmed at the school include "Revenge of the Slitheen", "The Lost Boy" and "The Nightmare Man".