A large and burgeoning literature has established that mastery goal orientations yield positive cognitive and behavioural educational outcomes. Less research has focused on the psychological antecedents of adopting mastery goals. The present study draws upon prominent psychological theories of achievement motivation, specifically the expectancy-value theory of Eccles, Wigfield and colleagues (Wigfield and Eccles 2002), to explore possible antecedents of students' mastery goals. Based on this theoretical framework, our study focused on children's perceptions of their competencies in English and maths and how these related to intrinsic value and mastery goals for English and maths. Questionnaires were used to gather data about Year 6 (N=60) participants' perceived competence, intrinsic value and mastery goal orientation, and correlational analyses established the direction and strength of the relationships between the perceptions. Participants were targeted for follow-up interviews (n=17) according to a matrix of low and high competence perceptions and mastery goals, with students selected from within each of six focal groups. Interview responses were reported according to emergent themes, from which we describe how the constructs under consideration relate to one another and highlight implications for educational practice.