Test bias within the field of psychometrics is an issue of concern in the South African context. In South Africa, after oppressive and discriminatory practices of the Apartheid era, certain tests were banned and considered invalid and unfair. Research is required in South Africa to investigate the effects and functions of psychometric tests in the context of the country's history and diverse population groups. This research investigated whether the Raven's Standard Progressive Matrices (SPM) is a good measure of non-verbal intelligence for high school children in the South African context, or whether it is biased by language and gender among Grade 8 and Grade 9 learners. The subjects were between 13 and 15 years old and attended an English medium government high school in Johannesburg. The archival data was collected over a two year period and the SPM was administered to some male and female subjects who either spoke English as a first language (EFL) and English as an additional language (EAL). A significant difference between the language groups in Grade 8 was observed and no significant gender differences were reported.