Science teachers have differing views about what students should learn. Their teaching experience often leads them to develop habitual answers to students' questions, such as--why should I learn this? Some teachers argue that students need to learn more "canonical" science knowledge so that they can become scientists, while others tell students to apply scientific knowledge in order to make their everyday lives easier. If a group of teachers argue and act in similar ways in similar situations, they can be described as working in a similar collective habit. In this study these are called "selective traditions in science teaching." In practical terms they work well in everyday, multifaceted, hectic teaching situations. However, the traditions can obstruct the inclusion of socio-scientific issues in national science education tests. Some research has been conducted on selective traditions in written curriculum material, although little is known about how they can be discerned in teachers' descriptions of their science teaching. This study draws on Dewey's discussion of the interplay between individual and collective habits to discern teaching traditions by regarding them as institutionalized teaching habits. A firmly developed analytical tool is applied to the extensive data consisting of twenty-nine Swedish science teachers' responses in semi-structured interviews. The methodology used in this study is inspired by earlier environmental and sustainability education research. The results are discussed in relation to earlier research on "scientific literacy" and how research can support teachers' changes of practice to encourage students to perform better in large-scale tests.