As an important carrier of teaching, primary school English textbooks play a vital role in students' interdisciplinary learning. This research attempts an in-depth discussion on the impact of interdisciplinary context in primary school English textbooks on education participants. The Primary School English textbook published by Tsinghua University Press as the research subject to solve the problems and current situations for interdisciplinary learning and teaching in primary English education. The objectives of this research are as follows. Firstly, to analyze the presentation of interdisciplinary content in the textbook. Secondly, to investigate the status of interdisciplinary learning and teaching in the classroom. Thirdly, to discuss the requirements of interdisciplinary learning for primary English teachers. This research is based on the theory of Content and Language Integrated Learning (CLIL). CLIL is mentioned as “a second language is used to teach certain subjects in the curriculum other than language lessons themselves” (Eurydice, 2006). With the deepening of CLIL pedagogies, the 4Cs Conceptual Framework was proposed to integrate content, communication, cognition and culture, which embedding language (communication) in CLIL processes in “using and developing language of learning, for learning and through learning” (Coyle, 2007). Although it is believed that CLIL is beneficial to language acquisition (Ruiz de Zarobe, 2015), and the CLIL program has been successful in most European systems, CLIL reliable research is still on the preliminary stage as a relatively innovative educational approach (Naves & Victori, 2010). The interdisciplinary approach seems to be appropriate to the CLIL contexts, in which cross-curricular connections among different disciplines are encouraged (Dobson et al., 2010; Segovia et al., 2010). Moreover, interdisciplinary “has become more central to knowledge” (Klein, 2002) and is the core of CLIL where language and content are integrated. Interdisciplinary learning is mentioned as processes that integrate information, data, techniques, tools, perspectives, concepts, and/or theories from two or more disciplines, usually in order to produce products, explain phenomena or solve problems in ways that are impossible to achieve by a single discipline (Boix Mansilla, 2006). Besides, the academy has become interdisciplinary and driven by the special needs of students in the information society (Catherine, 2017). The interdisciplinary learning in this studyrefers to the learning of interdisciplinary knowledge and abilities in primary school English textbooks, which can enhance students' abilities and sensitivity to interdisciplinary connections. The purpose of interdisciplinary learning in this study is to achieve the integrated development of language content learning, cultural understanding, communication, cognition and practical innovation based on the CLIL theory. At the micro-level of the research, with the clear focus on teachers and students as CLIL participants, methods and forms of classroom practice have not been widely discussed (Cenoz et al., 2014; Pérez-Cañado, 2012). Since CLIL is a relatively new trend in primary education, there are still scarce research results on young learners (Pladevall-Ballester & Vallbona, 2016). Besides, teachers need textbooks to use in the classroom, especially if they are beginners to CLIL teaching (Sasajima, 2019). The Compulsory Education English Curriculum Standards (2011) in China states that primary English textbooks should promote students’ abilities and strengthen links with other disciplines. The Primary School English textbook of Tsinghua University Press pays attention to cultivate students' interdisciplinary learning interests and improve students' comprehensive literacy, which basically reflects educational ideas of the Compulsory Education English Curriculum Standards (2011). Therefore, it is necessary to conduct in-depth research on primary school English textbooks from the interdisciplinary perspective based on CLIL theory, focusing on the participation of Chinese students and teachers in relevant educational activities, and to provide evidence support for international comparisons in Europe and other countries.

This study uses a combination of content analysis, questionnaires, and interview methods to achieve the following three research goals. (1) This study uses content analysis to quantitatively analyze the interdisciplinary content in the Primary School English textbook of Tsinghua University Press and uses qualitative analysis to describe and explain some units’ content. Based on the above analysis, this study collates and summarizes the presentation of interdisciplinary content in textbooks. (2) This study surveyed 127 students in the senior (5th and 6th grades) of the Tsinghua University Primary School in China and a questionnaire survey was conducted on the interdisciplinary implementation status and cognitive status of the Primary School English textbook of Tsinghua University Press. SPSS 20.0 statistical analysis software was used to describe the survey data in statistical analysis, multiple response analysis and cross-correlation analysis. (3) In this study, a semi-structured interview method was used for five English teachers from Tsinghua University Primary School (including teachers involved in the compilation of Primary School English textbook of Tsinghua University Press) and five researchers of primary English education major at the Primary Education College of Capital Normal University. This research carried out in-depth interviews and text transcriptions, coding from three dimensions: cognitive status, implementation status, and teacher requirements.

Primary school English education in China has a history of more than ten years. The necessity and feasibility of the combination of English learning and teaching with interdisciplinary education models have been recognized. From the research results, the textbook is rich in interdisciplinary content and the implementation of teaching materials still need to be further improved. The interdisciplinary content analysis of textbooks shows that the units have interdisciplinary content of different topics and the theme selection is diverse. Textbooks use ‘Text, Text Task, illustrations’ to achieve ‘Content and Language Integrated Learning’ and the integration of knowledge between English and other disciplines. From the proportion of humanities and social sciences and natural sciences, humanities and social sciences have a much larger proportion than natural sciences. As for the interdisciplinary implementation of textbooks, the results of questionnaire surveys show that most students believe that interdisciplinary teaching in primary school English is necessary and will increase English learning interest, as well as enhance multiple abilities. Most students are satisfied with the interdisciplinary content of the textbook and gained more knowledge in the humanities and social sciences than in the natural sciences. Moreover, teachers need to improve the integration of English with other subjects in the classroom. In addition, according to the results of cross-correlation analysis, students' grades and genders have differences in cognitive and learning interdisciplinary knowledge of primary school English. The interdisciplinary knowledge satisfaction with students in textbooks is an important factor affecting students' satisfaction with the overall design of textbooks. Interdisciplinary teaching places higher demands on the comprehensive ability of teachers. Finally, the suggestions are as follows: educators in different countries need to pay more attention to interdisciplinary development and learning situations; to correctly handle interdisciplinary content in textbooks, and to enhance teachers’ comprehensive quality to design lesson plans effectively.

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