Ethiopia has succeeded in rapidly expanding access to primary education over the past two decades. However, learning outcomes remain low among primary school children and particularly among girls and children from disadvantaged backgrounds. Starting with a systematic review of quantitative studies on the determinants of learning outcomes among primary school children in Ethiopia, this study then examined key determinants of students’ numeracy achievement over the 2018-19 school year. The study focused on Grade 4 children (N=3,353) who are part of an on-going longitudinal study. The two questions that guided this study are: what are the key determinants of numeracy achievement at Grade 4 in primary schools in Ethiopia, and how does our current empirical study contribute to understanding achievement differences in numeracy among primary school children in Ethiopia? We employed descriptive and inferential statistics to examine factors that determine differences in numeracy scores at the start and end of the school year, as well as determinants of numeracy scores at the end of the school year conditional on achievement at the start of the school year. We examined differences across gender, region, and rural-urban localities. We also used ordinary least squares and school ‘fixed effects’ approaches to estimate the key child, household and school characteristics that determine numeracy scores in Grade 4. The findings revealed that boys significantly outperformed girls in numeracy both at the start and end of the 2018/19 school year, but the progress in numeracy scores over the school year by boys was similar to that of girls. Besides, students in urban localities made a slightly higher progress in numeracy over the school year compared to their rural counterparts. Students from some regions (e.g., Oromia) demonstrated higher progress in numeracy over the school year relative to students in other regions (e.g., Addis Ababa). Key child (e.g., age, health, hours spent per day studying at home) and school- and teacher-related characteristics (e.g., provision of one textbook per subject for each student, urban-rural school location, and teachers’ mathematics content knowledge) were found to be significantly associated with student progress in numeracy test scores over the school year. These findings are discussed based on the reviewed evidence from the quantitative studies in Ethiopia.