Background: The role of homework in students’ academic performance is a widely debated topic about which there is no definitive answer. The objective of this study was to analyse the importance of parental help with homework in academic achievement, testing its cultural invariance (by country), academic invariance (by subject), and the stability of its effects over time.

Method: A meta-analysis was performed using the results of PISA evaluations from 2009, 2012, 2015, and 2018 from countries which applied the family PISA questionnaire. We analysed 180 effects and confirmed the fit of the model and the heterogeneity of the effects, performing an analysis of moderators and multimodal inference.

Results: Students who had more help with homework had lower academic achievement, with an overall effect (d) = 0.23, 95% CI [0.21, 0.25]. The effects were greater in Europe than in Asia. We did not find differences by subject type, and the results were stable over time.

Conclusions: Family help with homework does not ensure students’ academic success, and it is more important how that help is given than how much. This conclusion is valid for different types of subjects and is stable over time, with some variation between cultures.