This report presents the findings from an efficacy trial and process evaluation of the Parent Engagement Programme (PEP). The PEP was a school-level intervention designed to improve pupil outcomes by engaging parents in their children's learning. The programme was developed collaboratively by research teams from the University of Bristol and Harvard University and was delivered between September 2014 and July 2015. The study was conducted by the Centre for Effective Education, Queen's University Belfast between February 2014 and February 2016. The trial involved 15,697 students in Years 7, 9, and 11 from 36 English secondary schools, with schools sending an average of 30 texts to each parent over the period of the trial. The developers of the intervention managed its delivery to ensure optimal implementation. It was a cluster randomised controlled trial with randomisation at the Key Stage level, designed to determine the impact of the intervention on the academic outcomes of students in English, maths, and science, and the impact on absenteeism. A process evaluation used focus groups, telephone surveys, interviews, and an online survey to provide data on implementation and to capture the perceptions and experiences of participating parents, pupils, and teachers. Key conclusions include: (1) Children who had the intervention experienced about one month of additional progress in maths compared to other children. This positive result is unlikely to have occurred by chance; (2) Children who had the intervention had reduced absenteeism compared to other children. This positive result is unlikely to have occurred by chance; (3) Children who had the intervention appeared to experience about one month of additional progress in English compared to other children. However, analysis suggests that this finding might have been affected by bias introduced by missing data, so evaluators cannot reliably draw this conclusion. There is no evidence to suggest that the intervention had an impact on science attainment; (4) Schools embraced the programme and liked its immediacy and low cost. Many respondents felt that the presence of a dedicated coordinator would be valuable to monitor the accuracy and frequency of texts. Schools should consider whether they would be able to provide this additional resource; and (5) The vast majority of parents were accepting of the programme, including the content, frequency, and timing of texts. [Note: The post-reporting appendix was added in June 2017.]