As we all know, lead in is not only a teaching technique but also an important teaching step occurred at the very beginning of each class, so teachers are supposed to carefully design this step to activate students’ learning motivation.

 An old saying goes that: a good beginning is half done. Lead in, as the first step of teaching process, plays a rather significant role in teaching. So a good lead-in is essential to the whole English teaching. It shoulders the responsibility of teaching some basic English knowledge to students and provides students with the listening, speaking, reading and writing skills, as well as the obligation of carrying out their ideological education and cultivating their positive and healthy sentiment. 源'自:751]'论-文'网"]www.751com.cn

In ancient times, the Chinese famous educationist：Confucius said that “Gaining the new knowledge by reviewing the old”. It was perfectly in accordance with the constructivist learning theory formalized by Jean Piaget. They all stand for the idea that students can formulate the knowledge framework by building a proper connection between the old and the new language knowledge. So teachers should apply this theory to English classroom teaching closely. They need to create different lead in activities to activate students’ knowledge they learnt before so as to help them grasp the new one.  

Till now, experts have been exploring different lead in techniques to stimulate students’ interests in English learning and enhance the teaching effects. This thesis tries to discuss some fundamental principles such as relevance principle, instructiveness principle as well as some useful techniques such as listening to songs, asking questions and further explain how these techniques are applied to Junior English classroom teaching. 

2. Literature Review

The constructivist learning theory was formalized by Jean Piaget, it proposes that learning is a process on which the learner constructs meaning based on his own experiences and what he already knows. （Wang Qiang 2000: 6）

Constructivist learning theory contents two of the key concepts, which create the construction of an inpidual's new knowledge are accommodation and assimilation. Assimilating causes an inpidual to incorporate new experiences into the old experiences. This causes the inpidual to develop new outlooks, rethink what were once misunderstandings, and evaluate what is important, ultimately altering their perceptions. Accommodation, on the other hand, is reframing the world and new experiences into the mental capacity already present. Inpiduals conceive a particular fashion in which the world operates. When things do not operate within that context, they must accommodate and reframing the expectations with the outcomes.

John Dewey provided a foundation for constructivist. He believed that teaching should be built based on what learners already knew and engage learners in learning activities. （John Dewey 1974: 223）

This theory advocates the students-centered, teacher-guided teaching mode. That is to say, it emphasizes the learners’ status and strengthens teachers’ guidance at the same time. Instead of having the students relying on someone else's information and accepting it as truth, the constructivist learning theory supports that students should be exposed to data, primary sources, and the ability to interact with other students so that they can learn from the incorporation of their experiences. The classroom experience should be an invitation for a myriad of different backgrounds and the learning experience which allows the different backgrounds to come together and observe and analyze information and ideas. Students are the main body for information processing and meaning constructing. They must play a key role in the whole learning procedure.