Background: Integrated STEM approaches are acknowledged as important for making school subjects relevant and engaging for students and are reinforced with the current emphasis on computational thinking. Still, such approaches are rarely realized in schools. This study investigates how the traditional 'grammar of schooling' may prevent realization of more holistic teaching in line with ideas from integrated STEM. Purpose: A concrete teaching project where students design, program and build their own weather station is presented, and we investigate the values and challenges teachers see in the project and the obstacles that may prevent them from running it in class. This way it throws light on why STEM approaches may be difficult to realize in schools. Sample: The sample consists of teachers involved in a collaborative project in which Project Weather Station was developed, including the teacher who was undertaking the project in his grade 9 class. Design and methods: The study follows a case study design, with group interviews with teachers. Observation in class, video recording and interviews with students form a backdrop of the main interview data. Results: Results show that teachers see value in the weather station project in line with the overarching aims of the curriculum and consistent with STEM ideas. Challenges they see are related to own competence, time use, risk of failure and logistics across subjects. Conclusion: It is concluded that teachers' challenges reflect a tension between overarching aims in education and the more specific competence aims in the curriculum. On a systemic level there is therefore a need for an acceptance for the value of teaching that targets overarching aims of education. It is important to acknowledge teachers' challenges and fulfil their needs for support when undertaking extensive projects that have potential for realising the more holistic aims of education typical for STEM projects.