Enhancing achievement in mathematics involves overcoming barriers regarding discontinuity between school and other life contexts, motivational and other affective aspects, and language factors. The utility of cross-age peer tutoring using mathematical games and scaffolding of mathematical discourse in overcoming these barriers is explored in a study of prepost impact for both tutors and tutees. Participants were all the seven-year-old (n = 13) and 11-year-old (n = 14) pupils in a small, rural primary school. After matching and training of pairs, the project ran for five weeks, with two sessions of 30 minutes each week. Pre- and post-intervention, tutors completed the Me-As-Learner Scale (MALS), class teachers completed the Behavioural Indicators of Self-esteem (BIOS) scale with respect to both tutors and tutees, and tutors and tutees completed questionnaires on feelings and attitudes to mathematics. Verbal interaction in a sample of pairs was recorded pre- and post-intervention and analysed. Tutors participated in group subjective feedback discussions at mid-and post-intervention. Class teachers gave post hoc subjective evaluations. Tutors gained significantly overall on MALS and BIOS. Tutees gained significantly overall on BIOS. The tutor overall questionnaire gain was not significant, but the tutee gain was. Verbal interactions showed marked and significant increases in use of mathematical words, strategic dialogue and praise between partners, with a corresponding decline in procedural talk. Other qualitative improvements in interactions were evident, and subjective feedback from tutors and teachers was largely positive. This brief project appeared largely successful in increasing self-esteem for both tutors and tutees, and in increasing both the quantity and quality of interactive discussion about mathematics between children, as well as generic social and communication behaviours in the tutors. Questions remain about the longer-term duration of these gains, especially in different contexts. Recommendations for future research and practice are made.