In this article, we report on a study that examined the active and receptive English vocabulary of two different groups of Grade 3 learners in South African township schools. The groups consisted of English Home Language (HL) learners in the Western Cape and Xhosa HL and English First Additional Language (FAL) learners in the Eastern Cape. The purpose was to document their different vocabulary trajectories during Grade 3. The Woodcock-Muñoz Language Survey was used to measure the active vocabulary levels of 118 learners at the beginning and the end of the school year. Another 284 learners from the same eight Grade 3 classes participated in a receptive vocabulary test at the end of the year. This test assessed their knowledge of the 60 most frequent words that occur in South Africa Grade 4 English textbooks. Results showed that although the HL learners knew almost double the number of words their English FAL peers did, both groups of learners increased their active word knowledge through the year by about 9%. Regarding their receptive vocabulary, the English FAL learners on average only knew 27% of the most frequent words at the end of their Grade 3. No significant gender differences were found. Learners in both language groups who were above their grade age had significantly lower scores than their younger peers. This confirms findings that children who start school with weak language skills tend to stay weak. Finally, initial active vocabulary knowledge was found to be a strong predictor of vocabulary development during the school year.