This chapter argues that for quality teaching to be achieved, teachers must engage in professional training and development, which involves formulating and developing theories of their applied practice based on research and experience and which includes a critical reflection of actual data. An important component in what is acknowledged to be a complex multi-faceted task is the view that it is the quality of teacher problem solving and decision making that is a key variable in linking sound research to effective practice and thus supporting the raising of pupil standards and attainments. The 'scientist-practitioner approach' involves a conceptual stance by practitioners in which teaching methods and practices are informed according to valid and reliable evidence, either derived from the research literature or developed rigorously through the use of the scientific method within 'real-world' situations.

This chapter considers the role of experiments in regard to evaluation and action research in determining whether change in educational contexts can be attributed to the introduction of an intervention approach or programme. It explains the three classes of experimental design: 'true' experimental designs, such as randomised, controlled trials (RCTs), 'quasi-experimental' designs, and also 'small-n' experimental designs. True' and 'quasi-experiments' are 'studies of deliberate intervention. In the case of a 'true' experimental design such as an RCT, allocation to groups must be random. 'Small- n' experimental designs involve the manipulation of an independent (treatment) variable across a pre-intervention baseline phase, an intervention phase, and commonly a post-intervention phase. Most published studies of the effectiveness of school-based interventions use quasi-experimental designs. It is important for educational researchers to be aware of the beliefs and values of participants and stakeholders and indeed of underlying policy contexts and political realities.