每个学生都是不一样的个体。“因材施教”，针对不同孩子的特点提供差异化教学，促使每个学生都能在原有基础上获得发展，历来都是人类教育教学追求的目标。在寻求对学生开展差异化教学的历程中，分层教学是出现得比较早且发展历史比较长的一种教学形式，在我国、美国、英国等国家获得了较为广泛的应用。分层教学诞生的初衷是促进每一个学生都能在原有基础上获得更好的发展，让好学生“吃得饱”，学困生跟得上。然而多年的实践与研究表明，分层教学特别是班际分层教学产生的效果复杂且不确定，可能带来正面效果也可能带来负面效果。全面认识分层教学的效果，揭示其可能存在的负面效果，厘清分层教学效果产生的机制是促进分层教学发展的重要前提。国内外已有实证研究探索班际分层教学对学生特定发展维度的效果及其影响因素，但少有人同时探究分层教学的多种效果特别是负面效果，系统探索分层教学效果机制的研究较少，本土实证研究相对缺乏。

本研究旨在通过探索中学班际分层教学的效果及其产生机制，揭示班际分层教学的负面效果及其产生机制。围绕研究问题，本研究对北京市开展了班际分层教学的四所学校进行了调查。在对45名学生与18名教师进行深度访谈的基础上，研究采用扎根理论的方法对访谈资料进行了三级编码，获得了41个类属，14个初始范畴，6个副范畴；进一步形成了2个主范畴“中学班际分层教学对学生的影响”与“中学班际分层教学效果的影响因素”；在此基础上形成1个核心范畴“中学班际分层教学效果的产生机制”。研究采取了参与者检验、三角验证等方式确保研究的信度。研究的数据分析与理论建构同时进行，通过理论饱和的方式判定所建构理论的饱和度。基于上述研究工作，本研究发现：

第一，中学班际分层教学对学生的学业发展与心理健康发展都产生了影响。其中有关学业发展的影响涉及学习态度（含学业自我效能感、学习兴趣、学习动机与自主学习意识）与学业成就（含知识习得、学科能力与学业成绩）。有关心理健康发展的影响涉及学业情绪、自我认同（含身份认同与能力认同）以及同学的关系（含班际凝聚力与人际关系）。在上述维度中，分层教学既产生了正面积极的影响，也带来了负面消极的影响，且正面影响与负面影响几乎同时存在。

第二，中学班际分层教学效果的产生受分层制度、课程教学、重要他人与学生个人四类因素的影响。其中，分层制度包含组织形式、初次分层与分层流动三个要素；课程教学包含课程设计与教学实施两类要素；重要他人包含同伴互动、教师影响与父母影响三类要素；学生个人包含个体特征、学习策略与自我评价三类要素。在此基础上，研究辨明了各类影响因素内部及相互之间的作用，构建了中学班际分层教学效果产生机制的理论模型，揭示了分层教学对学生发展产生影响的方式与过程。

第三，中学班际分层教学对学生的学业发展和心理健康发展都可能产生负面效果，具体包含学业自我效能感与学习兴趣降低，学习动机与自主学习意识减弱，知识习得变差，学科能力与学业成绩降低，产生消极的情绪体验与自我不认同的态度，班级凝聚力降低，同学之间人际交往范围变窄与深度变浅。分层教学负面效果的产生是多种因素共同作用的结果，其原因可以归结为以下几点：分层教学对具有一些特征的学生带来了潜在的不利影响，且未对这些不利影响进行干预；分层与流动的依据不够合理；层内课程教学未进一步考虑学生的差异化需求；以及教师未提供针对性的支持或支持方式不利于学生长远发展。

本研究在以下三个方面取得了一定的创新：

一是建构了分层教学效果产生机制模型。基于系统化的视角，沿着分层教学的开展过程，通过追踪与回顾学生在分层教学不同阶段的体验与感受，本研究发现了影响分层教学效果的有关因素，厘清了不同要素的作用关系，形成了包含分层制度、课程教学、重要他与学生个人四类要素的效果机制模型，对分层教学在学生发展有关方面的不同效果做出了解释。

二是关注负面效果及其成因。已往研究少有人专门关注分层教学的负面效果及其成因。本研究在探索分层教学效果及其产生机制的基础上，厘清了中学班际分层教学对学生成长与发展多个维度可能存在的负面效果，并揭示了其成因。本研究回应了有关学者对教育领域开展负面效果研究的呼吁，是对教育措施负面效果研究的一种尝试，从相关问题的提出到研究的发现希望能对后续研究有所启发。

三是从避免负面效果的视角提出了分层教学实施的改进策略。根据本研究的有关发现，研究者从避免或最大程度减弱负面效果的视角出发，提出了中学班际分层教学实施的改进策略，为真实情境中开展分层教学并促进学生的差异化发展提供了有益的建议。

Every student is a different individual. “Teaching students in accordance with their aptitude” and characteristics in learning with differentiated instruction has always been the goal of teaching, and education. In the process of seeking differentiated instruction for students, ability grouping, emerged relatively early with a long history of development, has been widely used in China, the United Kingdom, the United States, and other countries. The original intention of ability grouping is to promote better development for each student on the original basis, so that both good students and students with learning difficulties may learn effectively and reach to their own full potentials. However, over the years of practice and research, it has been found that the effectiveness of ability grouping, especially between-class ability grouping, is uncertain with both positive and negative effects. There are empirical studies at home and abroad exploring the effects and influencing factors of between-class ability grouping on students' specific development dimensions. However, few have simultaneously explored the multiple effects of ability groupings. There is relatively little research on the systematic exploration of the effectiveness mechanism of ability grouping, and local empirical research is also comparatively lacking.

Focusing on the core question of “the effectiveness and generation mechanism of between-class ability grouping in middle school”, this study conducted a qualitative study in four schools in Beijing where the between-class ability grouping was implemented. Through in-depth interviews with 45 students and 18 teachers, the researcher used the Grounded theory method to code the interview data on three levels, and identifieds 41 themes, 14 initial theme categories, and 6 subcategories which further formed findings on two main topics: “the impact of middle school between-class ability grouping on students” and “factors influencing the effectiveness of middle school between-class ability grouping”. The findings on these two topics helped to achieve the research goal:  to explore and understand “the mechanism for generating the effectiveness of middle school between-class ability grouping.” The study adopted participant testing and triangular validation to ensure the reliability of the study. Data analysis and theory construction were implemented simultaneously until the saturation of the theory was achieved.

The study found middle school between-class ability grouping had an impact on students' academic development and mental health development. The influence of academic development involved learning attitude (including academic self-efficacy, learning interest, learning motivation and autonomous learning awareness) and academic achievement (including knowledge acquisition, discipline ability and academic achievement). The impact of mental health development involved academic emotions, self-identity (including identity and ability identification), and relationships with classmates (including class cohesion and interpersonal relationships). In the above dimensions, ability grouping had both positive and negative impacts, and both positive and negative impacts existed almost simultaneously.

Secondly, the effect of middle school between-class ability grouping was influenced by four factors: grouping institution, curriculum instruction, important others and students’ personal factors. Among them, grouping institution included three elements: grouping type, assignment to groups and mobility across groups. The curriculum instruction included two types of elements: curriculum design and instruction implementation; Important others include three types of elements: peer interaction, teacher influence, and parental influence; students’ personal factors included three types of elements: Individual characteristics, learning strategies, and self-evaluation. The study also identified the internal and mutual effects of various influencing factors, constructed a theoretical model of the mechanism for the effect of middle school ability grouping, and revealed the ways and processes in which ability grouping affects students' development.

Thirdly, the implementation of ability grouping in middle school classes may have negative effects on students' academic development and mental health development, including the reduction of academic self-efficacy and learning interest, weakening of learning motivation and autonomous learning awareness, deterioration of knowledge acquisition, reduction of discipline ability and academic performance, the generation of negative emotional experience and self-disapproval attitude, reduction of class cohesion, and narrowing and weakening the scope and depth of interpersonal communication between classmates. The negative effects of ability grouping were the result of multiple factors working together, and the reasons could be summarized as follows: ability grouping had potential adverse effects on students with certain characteristics, and no intervention had been made to these adverse effects; the strategies of assignment to different groups and mobility inter-groups were not appropriate; no further consideration was given to the differentiated needs of students in the same ability group; and the teachers did not provide pertinent support or the way of support was not conducive to the long-term development of students. 

This study is innovative in the following three aspects: creating and establishing a theory model of ability grouping mechanism with identified relevant factors that affect the effect of ability grouping. It clarified the relationship between different elements, and formed an effect mechanism model that includes four types of elements: grouping institution, curriculum instruction, important others, and students’ personal factors.

This study clarified the potential negative effects of ability grouping among middle school classes on multiple dimensions of student growth and development, and revealed its causes. As suggested by some scholars, this study explored and revealed the negative effects of educational measures. From the raising of relevant issues to the discovery, it is hoped that this research provides inspiration for future research.

The study also proposes improvement strategies of implementing ability grouping from the perspective of avoiding negative effects. Based on the findings of this study, the researcher proposed improvement strategies of between-class ability grouping by avoiding or minimizing negative effects, providing useful suggestions for carrying out ability grouping in real situations, so as to promoting students' differentiated development in middle schools.