Teaching is a complex profession. From planning to evaluations and classroom interaction with students, not to mention the administrative work that is part of a teacher’s duty. Everyday work consists of input from student/teacher relations in the classroom and also from the school organization, the policy documents and school laws and regulations, the media and, of course, from the teacher's own pedagogical knowledge and experience. This essay examines what factors play a key role when teachers make their decisions in the work of planning lessons. As a consequence, the research questions are:

- According to teachers, what factors do they experience affect their didactic choices while planning their work?

- What awareness does the teachers show when it comes to those factors that have an impact on their planning?

The method used for data collection is semi structural interviews with three Swedish teachers at an upper secondary school in Stockholm, Sweden. With a sociocultural perspective the teacher’s situation in school is framed as it illustrates a way to look at how knowledge is gained in the interaction between individuals in an institutional setting. Critical discourse analysis is used to identify and examine the key discourses that are at work in the interviews with these teachers. The conclusion is that all three teachers’ experience that three major discourses affect their planning: student’s needs, national policy documents and national testing and time factors. Both the planning of how work is organized in the classroom and the subject content is affected, but to different extents. To a certain degree all of the teachers express knowledge of the fact that their planning is affected by different factors. They feel that they are limited by national policy documents to the extent that they do not experience the curriculum to be as creative as they first envisioned it. They also express that a shortage of time is a factor that has negative impact on their work, explaining that they have too little time to plan their lessons. Each teacher also express that they very much adapt their teaching to meet their students’ needs.