Since the 1960s and early 1970s, many studies on classroom discourse have been undertaken in the English-speaking countries. A great number of them have drawn much attention to interaction between teachers and students. Among those who early began to conceive classroom talk in terms of structure were Bellack and his colleagues (1966). They offered a simple description of classroom discourse involving a four-part framework: 1) structure, 2) solicit, 3) respond, and 4) react (cited in Allwright and Bailey, 1991, 98).