A National Science Foundation-funded Mathematics and Science Partnership program, Leadership for Educators: Academy for Driving Economic Revitalization in Science (LEADERS), aimed to develop science teacher leaders who would influence the quality of science teaching in their respective schools. To fulfill a need to evaluate leadership abilities of teachers within LEADERS, a Teacher Leadership Instrument was developed based on our previous work. This paper examines the performance of teachers as outlined in the Teacher Leader Model (TLM) Standards following their enrollment in three teacher leadership courses aligned with these Standards. The study employed a qualitative approach to analyze peer professional development sessions provided by teacher leaders, and to rate leadership behaviours and practices. Results indicate that 31 of the 37 functions were exhibited by the teacher leaders, with most observations occurring at a developing level. Behaviours related to effective presentation and facilitation were observed most frequently, but the teacher leaders also incorporated research-based practices, information about assessments, and links to the community in their sessions. Further, these behaviours linked back to the intended outcomes of the three leadership courses. The results demonstrate one manner in which teacher leaders perform the functions of the TLM Standards in the context of professional development sessions.