Effectiveness Trial of Mastering Number at Reception and KS1 (Reception Focus), a Two-armed Cluster Randomised Trial

The National Foundation for Educational Research (NFER) has been funded by the Education Endowment Foundation (EEF) to perform a randomised controlled trial (RCT) of Mastering Number (MN) at Reception and Key Stage 1 (KS1). The RCT will focus on the Reception year group and investigate the impact of the MN programme on the maths ability of Reception pupils. The Mastering Number at Reception and KS 1 programme (referred to as MN) uses the National Centre for Excellence in the Teaching of Mathematics’ (NCETM) ‘teaching for mastery’ approach to develop a strong number sense among children in Reception, Year 1 and Year 2. The NCETM’s ‘teaching for mastery’ approach is underpinned by five ‘big ideas ’: coherent progression through the curriculum, careful selection of representations to expose mathematical structures, mathematical thinking and the use of mathematical language to communicate ideas, fluency and flexibility with mathematical concepts, and variation. These five ‘big ideas’ are embedded in the Mastering Number programme including the training provided to teachers and the materials and resources provided to deliver sessions to pupils. Training is delivered by NCETM and Maths Hubs, which are coordinated by NCETM. We employed a setting-randomised design, randomising primary schools in a 1:1 ratio into two groups, intervention and control, stratified by Maths Hub. Schools in the same Multi-Academy Trust were randomised together. Intervention schools receive MN, with Lead Teachers (i.e., teachers in each year group nominated to attend training prior to randomisation) receiving training in the 2025/26 academic year and delivering MN sessions over up to 31 weeks. Control schools do not access MN and continue with 'business as usual', which may include other programmes that aim to improve pupils' maths skills. The main trial cohort will be reception pupils in the Reception Lead Teachers' class. The primary outcome for the trial will be the total raw score from the Preschool Early Numeracy Screener – Brief (PENS-B) . The trial will also include a secondary outcome based on Early Years Foundation Stage Profile (EYFSP) profile data in the National Pupil Database. This will be a binary outcome determined by whether a pupil meets the expected level in both maths Early Learning Goals. Additionally, we will measure two further secondary outcomes: (i) Reception teachers’ knowledge/confidence with teaching mathematics and (ii) their beliefs about teaching mathematics. Separate from the main trial, we will also use a quasi experimental design (QED) to investigate the impact of 'embedding' MN (the additional impact after the first year a school uses the programme). This analysis will use a difference-in-differences design. The QED is largely separate from the main trial and uses a much larger (National) trial cohort. The impact (quantitative) analysis is the focus of this pre-registration, but will also be supported by an Implementation and Process Evaluation (IPE). The IPE will investigate fidelity of intervention delivery, usual practice, and assumptions around the causal mechanisms of the intervention. Additionally, a separate IPE strand outside of the context of the trial will explore the implementation and sustainability of MN in schools that are already delivering the programme.