Purpose: The purpose of this study was to provide an integrated analysis of a teacher's peer-teaching mediation strategies, the student-coaches' instruction, and the students' gameplay development across 3 consecutive seasons of sport education. Method: Twenty-six 7th-grade students participated in 3 consecutive sport education seasons of invasion games (basketball, handball, and soccer). The research involved 3 action research cycles, 1 per season, and each cycle included the processes of planning, acting and monitoring, reflecting, and fact finding. Data collection consisted of videotape and audiotape records of all 47 lessons, a reflective field diary kept by the first author in the role of teacher-researcher, and a total of 24 semistructured focus-group interviews. Trustworthiness criteria for assuring the quality of qualitative research included extensive data triangulation, stakeholders' crosschecking, and collaborative interpretational analysis. Results: Through the application of systematic preparation strategies, student-coaches were able to successfully conduct team instruction that resulted in students' tactical development and improved performance. Aspects such as the study of predominant configurations of players' gameplay and similar tactical principles across games within the same category prevented a setback in the complexity of the learning content addressed at the beginning of each season. Players also showed an increasing ability to adapt gameplay to game conditions. Conclusions: While sport education has the capacity to develop competent players, different levels of teacher guidance and learners' instructional responsibility are necessary when teaching tactics.