The development of collaborative Web applications does not follow a software engineering methodology. This is because when university students study Web applications in general, and collaborative Web portals in particular, they are not being trained in the use of software engineering techniques to develop collaborative Web portals. This paper presents a strategy for teaching collaborative Web portals based on reverse engineering and reuse mechanisms to engineer the collaborative Web portals' development. This strategy was successfully used in a final-year course of a Computer Science program at Carlos III University of Madrid, Spain. Its use has demonstrated an improvement in the maintainability of the Web projects developed as well as a decrease in the number of failures during the test phase. This is a very important step toward the engineering of Web applications. The students' grades for the same subject, with the same content and lecturers, also improved compared to those from previous years. The strategy, the details of its use, the results obtained after analyzing the projects the students developed, and their final grades are described in this paper. (Contains 15 figures and 11 tables.)