We report on our experiences on training to agile teamwork and software development our Computer science students in a software engineering class along two different academic years. The project developed by the teams consisted in building a Twitter client with special capabilities, whose requirements were (re)defined by the instructors during the course till the end of the project. We observed more than one hundred students divided in teams averaging five members each. We offered the students a complete software development environment including only open source tools for supporting agile collaboration and self-tracking. We asked the students to form their teams and then engage in team building activities, to help them to know each other better before starting their cooperation. We introduced the students to the agile vision using the Essence approach, which allowed them to tailor Scrum to their needs and guided them during the retrospectives. The main results we claim are: all teams were able complete all tasks in a timely manner; the use of an adaptable framework like Scrum has been well supported by the Essence approach to agile teamwork; the constraint to only use open source software tools hosted on premises added some difficulty to the students job, however all data and documents produced were available for inspection by the instructors; a product quality model and a team maturity model were useful to evaluate and compare the teams.