Few studies have evaluated the impact of mindfulness programmes on aspects of positive functioning amongst mainstream children and problems in design, sample size, and measurement are commonplace. The present study sought to address this and rigorously evaluate the impact of a 6-hour manualised mindfulness programme called 'Paws .b' on mainstream Primary School aged pupils' suppressing and sustaining attention skills, and their academic proxy measures.Two classes of Year-4 pupils (n = 30), their class teachers (n = 3), and a mindfulnessteacher (n = 1) were recruited from a mixed comprehensive Primary School.A quasi-mixed methods Randomised Control Trial (RCT) design with a quasi-experimentalintervention cross-lag was used. There were four data collection time-points 6- to 8-weeks apart. Pupils and class teachers were randomly assigned to the experimental group or the waitlist control group. Experimental pupils received a 1-hour Paws .b lesson per week for 6-weeks between baseline and Time-1; waitlist control pupils received Paws .b between Time-1 and Time-2. The remaining time-points acted as the 6- to 8-week and 14-week follow-ups. Quantitative data were gathered using teacher-reported and standardised attention measures, and teacher-reported academic proxy measures. Qualitative data were gathered using post-intervention pupil focus groups (FGs) and teacher semi-structured interviews.Within-condition comparisons revealed several significant pre- vs. post-intervention effects within the attention measures, the majority of which were maintained at one or both of the follow-ups, whereby several large estimated effect sizes were noted. Between-condition comparisons revealed a number of significant partial condition × time-point interactions within the attention measures. However, no significant effects were noted within the academic proxy measures. Positive and critically constructive evaluative themes were identified within the qualitative data.Findings were discussed relative to mindfulness and attention literature, and further implications for school implementation and future research were outlined.