This paper describes the development and assessment of a learning environment to support the transition of students from lower to upper secondary chemistry education in Germany. The learning environment centers on reviewing and expanding learners' prior chemistry knowledge in heterogeneous learning groups upon entering upper secondary education. The different learning materials are integrated in a computer-based learning environment, which offers a set of different learning stages which sequentially build upon each other. Another central element of the learning environment is an integrated test platform, which provides assessment and instant feedback to the students after completing each of the learning stages. This paper reports on the development of the learning environment by a group of teachers following the model of Participatory Action Research. Four schools and 81 students were involved in the implementation of the learning environment. Data sources used to reflect the learning environment were classroom observations, analysis of teacher feedback during monthly discussions, and a student survey. The study describes potential uses and reflects the benefits of using computer-based assessment within this learning environment from the viewpoint of the teachers and the students.