Rapidly changing technology means that graduates of engineering programs need to acquire important qualities of lifelong learning and self-learning to support a through-life ability to respond to advances in technology. At present, most of science and/or engineering programs at high schools and universities describe what the students are expected to know and be able to do by the time of graduation. These relate to the skills, knowledge, and behaviors that students acquire as they progress through the program to prepare graduates to attain the program educational objectives. The industry demands and expects from engineers a wide range of these generic skills in addition to a high degree of technical competence. This paper focuses on teamwork skill. Teamwork is the student outcome that means the ability to function on multidisciplinary teams. Teamwork is one of the most frequent ability involved in recent engineering courses, and takes part of many student-based approaches to learning, such as active methods, cooperative learning or problem based learning. The learning and development of teamwork is only possible if, as much as the scientific knowledge, their achievement is a self-building process of the student. The aim of the paper is to check if the use of rubrics for teamwork assessment is a useful method in terms of easiness and short time of application, and alignment with the active teaching approach adopted. A set of 51 Mechanical Engineering students were involved, during the fall semester of 2014, in the experience of developing a simulator of power plant with the Engineering Equation SolverTM software, EES. The power plant is a pulverized coal fired combined heat and power (CHP) plant. A term paper assignment was given to students, organized in teams of three members. The expected outcomes are the ability to perform the technical analysis of the power plant station in terms of mass and energy balances in different modes of work, and the development of personal skills such as data collection and analysis, problem-solving, critical thinking, teamwork, autonomous learning and the ability to apply theoretical knowledge to practice. A rubric was developed, intended to assess teamwork skill, with the requisite of being easy to understand by the students and short time consuming to fulfill it. Correlation between skill development and final team performance and grading is presented. Comparison with teamwork performance in other engineering courses is presented. The paper could be of interest to those readers that want to promote skill development in other science courses.