The primary aim of this study was to examine the vocabulary size of native speakers of English in New Zealand secondary schools. Two equivalent forms of the 20,000 version of the vocabulary size test were used in this study. Two hundred and twenty-seven 13-18-year-old native speakers of English at secondary school took an individually administered version of the test. The data from this study fits with the vocabulary size estimates for younger native speakers of Biemiller and Slonim ("J Educ Psychol" 93:498-520, 2001). The results suggest that most native speakers at secondary school have enough general purpose vocabulary to cope with their reading at school, and any deliberate attention to vocabulary should focus on subject-specific vocabulary.