The MathsFlip intervention aimed to improve the attainment of pupils in Years 5 and 6. The programme, developed by Shireland Collegiate Academy, used a 'flipped learning' approach involving pupils learning core content online, outside of class time, and then participating in activities in class to reinforce their learning. The programme used an online learning environment which provided teachers and pupils with resources for learning mathematics outside the classroom, allowed collaborative communication between colleagues and pupils, and provided information to teachers on pupils' progress prior to planning and teaching a lesson. Staff from Shireland trained Year 5 teachers from 12 primary schools in the West Midlands over two days and provided some ongoing support. The project was a randomised controlled trial involving 24 schools: 12 schools received the intervention from April 2014 until April 2015 using MathsFlip to deliver lessons at the start of a new maths topic for the cohort of pupils in Year 5; 12 schools acted as control schools delivering maths lessons in the usual way. Impact was measured using pupils' Key Stage 2 (KS2) maths scores in summer 2015. The process evaluation involved lesson observations and collecting teachers' and pupils' perceptions of the programme through interviews with staff, focus groups, and online teacher surveys. Among the key findings were: (1) Children in MathsFlip schools made the equivalent of one additional months' progress in maths, on average, compared to children in comparison schools; (2) The impact on maths was slightly higher for children eligible for free school meals ('FSM pupils') than for all children in the trial; and (3) The majority of teachers in the trial were very positive about the flipped learning approach and the technical and professional support they received from Shireland staff.