In 21st century education students should have ample opportunities to collaborate on authentic problems. Many teachers however find it difficult to make the transfer from teacher to student-centered education. Giving students autonomy can be disquieting to teachers, as they fear to lose control of student learning. Teachers in a teacher development team developed context-based student learning material on the topic "salts." Self-regulating student cooperative groups would work autonomously during a number of weeks using this material. To monitor the "what and how" of these groups, a student group log was developed. In this log all the work the group performed in class had to be noted and during each lesson a number of questions to stimulate interaction and reflection had to be answered. This research describes how students and teachers used and perceived the group log during their cooperative journey when studying the material on "salts." The results show that students were positive, and especially appreciated teachers' quick feedback. The log stimulated student interaction, guided the learning processes, and stimulated student reflection. To provide feedback, teachers needed between 3-5 minutes per log after each period, and stressed that this was well invested time as they could now monitor student progress.