Compliance to government-prescribed national 'school-readiness' performance measures, particularly in early numeracy and literacy, readies and governs early years children for primary schools' test-based culture. Performance measures, such as the Early Learning Goals and the Phonics Screening Check, govern and steer early years teachers towards inappropriate ability-grouping practices to obtain required outputs and results. This research draws on the findings of an English nationwide survey of early years and primary Key Stage 1 teachers (n = 1373), four focus groups and four case study schools with 12 in-depth interviews. Early years teachers' attempts to meet nationally imposed school-readiness performance measures are analysed as Foucauldian governance. Finally, the article examines ability-labelling and ability-grouping impacts on children's well-being and aspirations.