Background: Research has provided evidence about the negative impact of school bullying on the academic performance of primary school children, but studies on the prevalence of school bullying and numeracy performance of children are very scant. Aim: This study aimed to investigate the prevalence of school bullying and numeracy performance among primary school children, and its implications for school-based interventions. Setting: The sample comprised 435 children (56.3% females and 43.7% males; Grades 1-7; median age = 11 years) attending six primary schools in three different education districts in Johannesburg, South Africa. Method: The children self-reported their experience of bullying by peers through a questionnaire. In addition, they completed numeracy tests. For children aged 6 to 9 years, the questionnaire was completed with the assistance of trained field workers. Results: The results following a linear regression with multiple predictors indicated that numeracy was significantly associated with contextual variables such as grade and home language. Bullying was strongly associated with socio-economic indicators such as school quintile and regional situation. These variables are important in early school support interventions directed at improving learner numeracy performance in the primary school. Conclusion: The results show a relatively high percentage of bullying in primary schools in the Johannesburg region. The performance in numeracy was significantly associated with the grade and home language of the learner. Contextual variables related to socio-economic situation of learners such as school quintiles and regional situation had strong associations with bullying.