In 1999 Stigler and Hiebert made a phenomenal international impact on educators, especially in the US with the publication of their book, The Teaching Gap. Their findings clue to understanding the substantial gap between the US and the Japanese mathematics achievement scores in the Third International Mathematics and Sciences Study (TUMSS). Hey claimed that despite the introduction of group work and the apparent belief among American teachers that they had adopted a social constructivist pedagogical (Hiebert and Stigler, 2000).In addition, they found few changes in teacher’ goals toward deeper mathematical understanding (Hiebert and Stigler, 2000) Educators and policy and useful to the perhaps LS might be the key to explaining this disparity and useful to the design of curriculum reform in schools (Council for Basic Education,2000; Fernandez and Yoshida, 2002). This was during a period when national education in the US was in crisis with many pressing issues needing to addressed. LS began to make inroads into teacher education programmes and serious attention was paid to testing it on an academic level.
Under these circumstances and in combination with the call for professional development that is more school-based and grounded in daily realities, scholars introduced lesson study as a Japan professional development method, denouncing conventional one-time activities professional development approach (Lewis and Tsuchida, 1998;Stigler and Hiebert,1999).