This study examines the pooled effects of Education Endowment Foundation (EEF)-funded trials on literacy and mathematics attainment outcomes for pupils with English as an Additional Language (EAL), focusing on their time since arrival (TSA) into the United Kingdom (UK) schooling system. In general, EAL pupils are a highly diverse group, and as noted by Hutchinson (2018), their educational attainment often depends on how long they have been in the UK schooling system. Pupils with lower values of TSA, meaning they entered the system more recently, tend to have lower baseline attainment (Hutchinson, 2018), particularly in English. Research by Strand and Lindorff (2020, 2021) and Demie (2018) also found that English proficiency and attainment scores are strongly influenced by the time pupils have spent in the schooling system. Late arrival EAL pupils often face significant challenges due to limited exposure to both the curriculum and the English language. These challenges are more pronounced in literacy outcomes, as mathematics relies less on language proficiency. Using the EEF data archive, the research objectives of this study were to examine the overall pooled effects of both mathematics and literacy EEF-funded trials on EAL pupil attainment, the differential effects between EAL and non-EAL pupils, and to understand how EAL pupil attainment impacts varied depending on the pupil's time of arrival in the UK education system. [This project was co-funded by The Bell Foundation.]