There is a general consensus in the research about factors characteristic of effective teacher professional learning. Recent reports highlight the significance of factors such as intensive and sustained professional development, focus on specific academic content, strong working relationships among teachers, and alignment with school improvement goals and priorities. Investigations of the links between the enhancement of teachers’ knowledge and practice resulting from professional learning activities, and improvements in students’ learning raise a number of key research questions. Evaluation studies designed to identify features of successful professional learning programs designed to improve literacy learning typically address research questions such as: • What impact has the program had upon the understandings, confidence and teaching skills of participants? • What has been the impact of the program on the literacy achievements of students in participating schools? • To what extent has the capacity of participating teachers to support student learning in literacy improved? • To what extent has the capacity of participating schools to support and sustain student literacy outcomes improved? • What were the factors critical to the success of the initiative? For those undertaking such evaluations, questions about the nature of evidence that might provide answers to these questions are of paramount importance. These questions centre on the chain of logic that connects professional learning activities, enhanced teachers’ knowledge, improvements in teaching practice, and improvements in students' literacy learning. Links between teachers’ professional learning and student learning outcomes are elusive, and the task of finding evidence of links between teachers’ learning and students’ learning presents significant challenges. A key challenge involves ways of capturing the chain of impact from the changes to teaching practices brought about by professional learning activities to changes in student learning outcomes. Evidence of these changes is often more likely to be found in longitudinal investigations. This paper reviews several evaluation studies of large-scale professional learning initiatives provided by education systems, as well as school-based professional learning initiatives. All programs discussed focussed on improving literacy learning. The review focuses on the effectiveness of the strategies used in these evaluations to gain insights into the impact of the teacher professional learning initiatives on students’ learning. The studies selected all provided opportunities for gathering evaluation information over extended periods of time, between one and two years. Each evaluation study was designed to include a focus on the impact of the professional learning initiative on teaching practices and student learning.

This paper takes the form of a review of several evaluation studies in which evidence of the impact of the professional learning program about teaching and learning literacy was gathered over extended periods of time, ranging from one to two school years. The review will address questions regarding the collection of evaluation information, and the interpretation of tis information. The review will take particular account of the nature of changes in teachers’ knowledge and practice. If the impact of professional development is to be judged in part by its impact on student learning, a longitudinal view of change is needed. Teachers taking up new practices may see evidence of improvement in their students’ learning from an early stage, but it may be two or three years until the new practices are firmly embedded in their teaching, and before evidence can be collected that shows sustained difference in students’ learning.

The strategies used to gather evidence over time in these studies are described. These strategies take account of the design and purposes of different programs of teacher professional learning. Data collection strategies selected included the collection of responses to surveys on more than one occasion, observations and interviews in schools, and the collection of evidence of student achievement. The challenges of collecting this range of evidence and some findings from these evaluation studies will be discussed. In particular, the challenges encountered in linking teachers’ professional learning to students’ learning will be explored. These challenges include the need to align evidence of student achievement with the scope of teachers’ learning in a particular initiative, as well as the need to employ a broad range of achievement data to provide insights into improved student literacy achievement.