Testing knowledge is an integral part of a summative assessment at schools. It can be performed in many different ways. In this study we propose assessment of physics knowledge by using a class tournament approach. Prior to a statistical analysis of the results obtained over a tournament organized in one of Polish high schools, all its specifics are discussed at length, including the types of questions assigned, as well as additional self- and peer-evaluation questionnaires, constituting an integral part of the tournament. The impact of the tournament upon student improvement is examined by confronting the results of a post-test with pre-tournament students’ achievements reflected in scores earned in former, tests written by the students in experimental group and their colleagues from control group. We also present some of students’ and teachers’ feedback on the idea of a tournament as a tool of assessment. Both the analysis of the tournament results and the students’ and teachers’ opinions point to at least several benefits of our approach.