Mr Costa was the head teacher of Heathcroft High School in Noughts and Crosses. As with many people at the time, he was extremely prejudiced against Noughts, and only included them in his school because he was forced to by the Government.
He turns a blind eye to the hostility that the Noughts face at his school, even when Shania is seriously injured. He is seen arguing with Mrs Paxton when the Noughts get isolated, saying that no one wanted them there in the first place. He later expels Shania for fighting, and 'suspends' Callum over his father's terrorist accusation, although Callum suspected that Mr Costa had no intention of ever letting him return. At some point after this, Mr Costa left the school and was replaced by Mrs Paxton.
In his first appearance, he was referred to as 'Mr Corsa' but has always since been called 'Mr Costa'.