Teachers interpret and enact policy of various sources from national steering documents to local policy and curriculum resources. This study targets the curriculum resource of Naturvetenskap och teknik för alla (NTA), a resource developed to strengthen middle school science education in Swedish schools. This study examines how use of NTA mediates teachers’ didactic considerations when navigating issues of standardisation and professional autonomy. The research question targets how teachers achieve professional agency in this process. This study is based on case studies with four teachers using observations and semi-structured interviews. Theoretically, the analysis is guided by the ecological model of teacher agency. The findings show that the teachers adapt resources to reflect their instructional goals and objectives, and their students’ needs. The results reveal that the NTA resource both contribute to and constrain teachers’ agency but also that the teachers emphasise the projective dimension when reflecting on their work.