Discussions on class size, in the past, were mainly based on findings of research studies conducted in the United States, and experience of small class teaching in Shanghai and East Asia. Prof Galton, however, presented in this seminar his team's findings of a large scale study to develop and evaluate effective group work at the primary and secondary school levels in the United Kingdom. It found that, among other results, students of different ability groups all benefited in a class of 25. Moreover, he also emphasized the importance of enhanced teacher training in order to get the optimum benefit from the lowering of class size.