In this study, 34 trials of formal formative assessment activities in the context of inquiry-based science education (IBSE) from Swiss primary and upper secondary school teachers will be analysed. The aim will be to explore the formal formative assessment activities implemented in IBSE at different school levels. The trials (14 from primary school, 20 from upper secondary school) are documented with teaching plans and teaching materials as well as with transcripts from individual interviews. For the analysis, the trials were coded with a deductively developed coding scheme involving categories specifying the inquiry characteristics of the trials as well as the formative assessment characteristics. Overall, the empirical results suggest that at primary school level, more extensive formative assessment practices are possible, such as the combination of several methods within the context of one inquiry unit. At upper secondary school level, formative assessment practices are more straightforward and closely linked to summative assessment practices. These differences will be used to develop characteristic features of formative assessment practices for the two school levels.