The aim of this article is to explore how children use and reuse semiotic resources in their writing of hybrid genres in school. In focus are children’s use and reuse of semiotic resources from both earlier literacy events at school and literacy events they have experienced at home or in their leisure time. This double focus is rare in previous studies and thus the study contributes new insights concerning how children’s writing can be understood as a hybridization process in which semiotic resources from different literacy practices in school and out of school interplay. The theoretical framework of the study is based on New Literacy Studies, social semiotics and genre theories. The methodological approach is semiotic ethnography. The material is based on videotaped classroom observations of a particular writing process consisting of both collective and individual writing, as well as on the texts produced. A genre analysis is conducted in three steps, in order to explore the reuse of semiotic resources from literacy events in and out of school in five children’s texts. The results of this analysis show children’s creative ways of reusing semiotic resources, not only from literacy events and practices outside of school but also from previous literacy events in school. These creative ways of children engaging in hybridization processes while writing a narrative in sub-genres within an official literacy event in school can be understood as the children seizing agency in order to influence their own practice. © The Author(s) 2017.