Unfortunately not much has been done in this area which makes it a great research topic. I am currently working on one similar project with my colleague.
The following might be a good resource for you although it is 5 years old:
Teachers as Leaders in Education Reform. ERIC Digest. Wynne, Joan
Although the above article itself might not be too informative, it will lead you to several good references.
I can point you towards two more good articles, quite recent, which might be good resource for you. However, these are more on the HOW part of teacher leadership.
I may be able to recommend a couple of more later.
1. Leading from the Front of the Classroom: A Roadmap to Teacher Leadership that Works. 2014. The Aspen Institute and Leading Educators.
2. A Culture of High Expectations: Teacher Leadership at Pritzker College Prep
2014. The Aspen Institute and Leading Educators.
I hope you would be able to locate these. If not, then let me know. I have these with me.
The need for close attention to curriculum and pedagogy and the importance of having a designated leader in an area.
The role of the educational leader, is based on some of the experiences of a small group of early childhood educators who have been meeting regularly over the past two years to discuss ideas about their leadership and share their successes and challenges. The group comprises educational leaders from UTS Childcare—Blackfriars, Magic Pudding and Kids Campus, the University of NSW (UNSW)—Tigger’s Honeypot, and Marrickville Council’s Cavendish Street and Tillman Park Early Learning Centres.
A little closer to home please see the ongoing work of the HertCam Network hertscam.org.uk for stories, papers and articles relating to the impact of development work initiated and led by hundreds of teachers in their own schools over the past decade. A recent book publication can be found in the faculty or I can lend you a copy.
Not sure if you are looking specifically for teacher leaders or for leaders within a school. There is a lot of research on how leaders within a school impact student learning. Here is one. I am working on a paper that looks at how/if science coordinators in a district impact teacher learning and subsequently student learning.
There are a range of publications by Larry O'Toole and Ken Meir in Public Administration Review and other top level journals on the impact of management and leadership on school district performance in Texas. This is extensive, thoughtful, and robust research, based on a large data set, with longitudinal dimensions as well.