Much research has been conducted on children's self-talk and its use to regulate thinking and behaviour, but research has typically been conducted on audible self-talk when undertaking specific tasks designed by researchers and in laboratory situations. Addressing the need to study self-talk in the classroom and by students of an age when self-talk is largely internalised, this study investigated the association of self-talk with children's self-regulatory behaviour and academic performance. The findings reported in this paper are based on the data from self-report questionnaires on self-talk completed by eight-to-nine-year-olds, national mathematics achievement test results, and a teacher-completed behaviour rating scale. Based on the previous research, results were somewhat unexpected, including that self-talk may not have a very strong role in children's behavioural self-regulation and calling into question an effect of self-talk on children's learning in the classroom. Possible reasons are provided and the need for future research is acknowledged.