Vocabulary knowledge is crucial for accessing the school curriculum and for performance on school assessments. It is also strongly influenced by a child’s exposure to language in the home and disadvantages in knowledge are apparent at school-entry. Vocabulary knowledge has a lasting influence on academic achievement that persists into secondary school and disadvantages are only partially ameliorated by teacher-directed instruction. Reading ability is also crucial for academic achievement, but contrasts with vocabulary as a skill in which initial disadvantages tend to fade over time. We followed primary-aged pupils from the Aston Literacy Project (a large longitudinal study of reading from school-entry to late-primary) during the critical but under-researched transition to secondary school. This data set includes information on children’s vocabulary, word reading and reading comprehension at the and of primary school and the beginning of secondary school. The data were used to examine reading and vocabulary development across the primary-secondary school transition.Vocabulary knowledge is crucial for accessing the school curriculum and for performance on school assessments. It is also strongly influenced by a child’s exposure to language in the home and disadvantages in knowledge are apparent at school-entry. Vocabulary knowledge has a lasting influence on academic achievement that persists into secondary school and disadvantages are only partially ameliorated by teacher-directed instruction. Reading ability is also crucial for academic achievement, but contrasts with vocabulary as a skill in which initial disadvantages tend to fade over time. We followed primary-aged pupils from the Aston Literacy Project (a large longitudinal study of reading from school-entry to late-primary) during the critical but under-researched transition to secondary school. We examined whether the transition to secondary school and whether participant level characteristics such as SES affected their vocabulary and reading development during this time. For data collected from this sample between 2011-2016 see: 10.5255/UKDA-SN-852671