South Africa's rich multicultural society is reflected by 11 official languages. The Language in Education policy stipulates that children should start learning at school in their home language until Grade 3. In most schools, the language of instruction for all subjects changes in Grade 4 from an indigenous African language to English, which means that more than 80% of South African pupils learn in a language different to their home language. This paper seeks to ascertain (a) to what extent South African pupils are proficient readers in the language in which they have received reading instruction for 4 years, (b) what differences in achievement become evident between pupils in Grade 4 and Grade 5, and (c) the relationship between South African pupils' performance in the test language and home language. Statistics from the Progress in International Reading Literacy Study (PIRLS) 2006 were applied to determine differences in achievement.