In many countries, children with low socio-economic status and with migration backgrounds are particularly disadvantaged in terms of their educational opportunities. Despite different forms, many extended education offerings around the world pursue a common educational focus, namely supporting the development of all students while reducing educational disadvantage related to social status, migration background, or any other diversity dimensions. Research shows that the process quality of extended education offerings is crucial for their effectiveness. This study examines experts' understanding of the process quality of extended education offerings that are particularly beneficial for primary school children from disadvantaged backgrounds. The data comes from problem-centred expert interviews with researchers from 16 countries worldwide. Structuring qualitative content analysis identifies three quality dimensions that are emphasised by the experts: (a) principle of educational processes: interests- and needs-orientation, (b) formats and methods: variation, and (c) interactions between staff and children: appreciation and (learning) support. The identified dimensions highlight the crucial additional value of extended education compared to formal lessons and underline the relevance of embedding social-pedagogical principles in the diversity-sensitive design of extended education offerings to support children from disadvantaged backgrounds.