案例背景课堂教学本来应是有计划、有目的、有组织的教学活动,教师在教学之前要对课堂进行精心预设。而实际的课堂是师生、生生不断交往互动的场所,是教师与学生个体或群体之间的知识、个性、情感不断碰撞、整合、调适的场所。所以,课堂的变化却是无常的。这节课教师设计的再完美、再合理、时间的分配再恰到好处,也比不上学生的学习所需。因此,实际课堂的教学往往是“变化无常”的,教师只能“随波逐流”。但是,教师是舵手,要根据课堂的情 Case Background Classroom teaching should have been a planned, purposeful and organized teaching activity. Teachers should make careful preparation of the classroom before teaching. The actual classroom is a place where teachers and students interact constantly with each other. It is a place where teachers, students, or groups of individuals constantly collide, integrate and adjust their knowledge, personality and emotions. So, the changes in the classroom are impermanent. This class teachers designed perfect, reasonable, time distribution and then just right, but also less than the students need to learn. Therefore, the actual classroom teaching is often “changeable impermanence ”, the teacher can only “drifting ”. However, teachers are helmsman, according to class situation