The use of Virtual Reality (VR) in education is getting more and more common, especially when hands-on learning experiences have to be delivered. With VR it becomes possible, e.g., to simulate dangerous or costly procedures that could hardly be implemented in real settings. However, engaging large classes in immersive laboratory activities may be difficult, since VR kits are still rather expensive for quantity purchases and may require powerful PCs as well as proper spaces to work. A possible way to deal with these issues could be to combine VR with so-called asymmetric Collaborative Learning (CL). CL is a particularly interesting pedagogical approach, as it make learners work in team to achieve a common educational goal, promoting critical thinking and active learning. In asymmetric CL, in particular, learners use different technologies to interact. When combined with VR, asymmetric CL could be used, e.g., to let some learners get immersed in a virtual environment, while some others actively participate in the experience using a desktop interface. This configuration could allow, in principle, to involve more learners in the same amount of time and with the same number of VR kits, while also letting them benefit of the advantages of CL. Based on these considerations, this paper investigates the impact of CL on VR-based education by leveraging an immersive virtual environment designed to support a laboratory experience in a Chemistry course. A user study was conducted by involving 46 university students enrolled in the course. Objective and subjective metrics were used to compare two education methods, i.e. one in which the students experienced the VR environment in isolation, another one in which pairs of students collaborated with an asymmetric approach. Students' knowledge acquisition was assessed by means of theoretical quizzes, whereas practical performance was automatically measured during the VR experience. The experimental results showed that trading off VR-based, individual learning for CL may have positive effects on the acquisition of theoretical knowledge, but may be detrimental to the achievement of practical abilities if sufficient exposure to technology cannot be guaranteed.