This article reports the development, validation and use of an instrument designed to provide teachers with feedback information, based on students' perceptions, about their classroom environments. The instrument was developed to provide teachers with feedback that they could use to reflect on their teaching practices and, in turn, guide the implementation of strategies to improve their learning environments. To determine the validity and reliability of the new instrument, data from 2043 grade 11 and 12 students from 147 classes in 9 schools were analysed. The Rasch model was used to convert data collected using a frequency response scale into interval data that are suitable for parametric analyses. During an action research process, reflective journals, written feedback, discussions at a forum and interviews with eight teachers helped to illuminate the processes used by teachers during action research. This article reports the views of these teachers in general and examines more closely how one of the teachers used student responses to the learning environment questionnaire as a tool for reflection and as a guide in transforming her classroom environment. This case study helped us to gauge the extent to which action research based on students' perceptions of the learning environment was useful in guiding teachers' improvements of their classroom learning environments.