According to the National Science Standards, science educators have been calling for the inclusion of inquiry-based approaches in science classrooms as a reform for science instruction. Teachers' reluctance to implement inquiry-based approaches may be attributed to the different interpretations of the underpinning theory. Any efforts to help teachers implement effective teaching approaches, therefore, should not target merely additive skills; rather, such efforts should foster fundamental changes of beliefs, knowledge, and habits of practice that teachers deeply hold.;This study is a part of a bigger project known as the Science Writing Heuristic (SWH) Partnership Professional Development Project, conducted at Iowa State University in association with the Iowa Department of Education to help improve science teaching. The aim of the project is to help in service science teachers understand and apply a student-oriented instructional approach, using the SWH. The framework of the SWH emphasizes the role of classroom dialogical discussion in students' learning. The role of the teacher when implementing constructivist approaches represented in a student-oriented instruction, differs markedly from traditional approaches, and hence there is a need to study the changes in teaching practice when using this specific tool.;The methodological framework of this study combined qualitative and quantitative methods. Interpretative case studies for 18 science teachers are presented. A triangulation strategy was used to provide support for the qualitative findings using three different data collection approaches: observation, questionnaire, and interviews. Quantitative data in the form of student performance on higher order conceptual questions and total test scores were collected.;Teachers varied in their implementation of the SWH. Three criteria were constructed to define teachers' levels of implementation: epistemological belief, pedagogical practice, and teacher content knowledge. Different components were included within each criterion, with three scales used to rank each teacher's implementation within each criterion.;The study is pointing to the importance of assisting science teachers with effective pedagogical strategies if there is to be an impact on students' performance on tests. This project was undertaken with partnerships between schools, Area Educational Agencies, and the University. Such partnerships need to be built to promote successful change to science teaching.