This paper investigates whether teacher strikes affect student achievement at the primary school level in South Africa. A cross-subject analysis with student fixed effects is used to eliminate sources of endogeneity bias at the school and student level. Results indicate that teacher strike participation negatively affects learning for students in the poorest three quarters of schools in South Africa. A negative effect size as large as ten per cent of a standard deviation is observed. There is also evidence that more marginalised students, both in terms of socio-economic status and academic performance, are affected most negatively by strike action. However, application of a technique by Altonji, Taber and Elder (2005) indicates that it is not possible to rule out that measured strike effects may be driven by omitted variable bias. The student fixed effects strategy fails to adequately control for unobserved teacher characteristics that may influence both a teacher’s decision to strike and student achievement.