为增加中西部农村地区的教师供给，提升农村地区的人力资本积累，我国近年来实施了一系列的农村师资补充政策。中央政府2006年启动实施的农村义务教育阶段学校教师特设岗位计划（以下简称“特岗计划”）便是其中实施范围最广、影响力最大的政策之一。“特岗计划”实施以来，各级政府给予了大量的财政投入。然而，尽管国家财政投资巨大，但目前关于该政策实施效果的评价研究却非常有限。综合来看，已有研究大多仅停留在定性或描述阶段，缺少根据投入-产出框架从学生学业成绩进步的角度对政策作出定量评价的实证研究。因此，本文以教师对学生学业成绩提升效果作为教师教学质量的衡量指标，从特岗教师与非特岗教师对学生学业成绩影响效应差异的视角，考察了“特岗计划”政策的实施效果。

具体来看，本文基于委托-代理理论提出研究假设，利用包括300所农村初中、600名数学教师和33471名样本学生的大规模调查数据，对特岗教师与非特岗教师教学质量的差异进行了考察；同时，为保障估计结果的有效性，本文不仅基于准实验的研究设计手段，对评估结果进行了多维度的稳健性检验和异质性分析，而且基于非认知技能为结果变量就特岗教师教学质量问题开展了深入讨论；在此基础上，围绕特岗教师教学质量并没有表现出优于非特岗教师的结果进行了理论探讨与实证检验。

本文的主要研究发现如下：第一，尽管特岗教师在学历方面显著高于非特岗教师，但相比非特岗教师所教班级，特岗教师所教班级的平均成绩不仅没有显著的更高，甚至表现为非显著地低于非特岗教师任教班级。第二，本文进一步以非认知能力指标作为因变量，同样发现相比非特岗教师所教班级，特岗教师授课班级学生在数学学习焦虑、学习动机等方面没有显著差异。第三，异质性分析表明，相对于家庭社会经济地位较好的学生，特岗教师授课会降低家庭资产排名在后25%学生的数学成绩。第四，基于委托-代理理论分析了政策失真的可能机制，发现特岗教师在学生课外辅导时长上显著低于非特岗教师，为教学付出的时间和精力不如非特岗教师。进一步，追踪调查发现，特岗教师流失现象严重，有近一半的特岗教师流入县市中小学，据此可以推测，“骑驴找马”的现象可能广泛存在于特岗教师群体。因为没有安心在农村任教，特岗教师难以把精力放在提升学生成绩上，因而他们也没有在教学质量上表现出更优，这大大制约了特岗教师政策的实施效果。本文为政策进一步的修订提供了实证的证据支持。

In order to increase the supply of teachers in rural areas in the central and western regions and enhance the accumulation of human capital in rural areas, China has implemented a series of rural teacher supplementary policies in recent years. The Specially contracted plan for teachers in rural compulsory education stage (hereinafter referred to as the “Specially Contracted Teachers Plan”) initiated by the central government in 2006 is one of the most widely implemented and influential policies. Since the implementation of the "Specially Contracted Teachers Plan", governments at all levels have given a lot of financial input. However, despite the huge national financial investment, the current evaluation research on the implementation effect of the policy is very limited. Taken together, most of the existing research only stays in the qualitative or descriptive stage, and there is no empirical research on quantitative evaluation of policies from the perspective of student academic performance progress based on the input-output framework. Therefore, this article takes the effect of teachers 'improvement on students' academic performance as a measure of teachers 'teaching quality, and examines the implementation effect of the " Specially Contracted Teachers Plan " policy from the perspective of the difference between the effects of Specially Contracted Teachers and general teachers on students' academic performance.

Specifically, this paper proposes a research hypothesis based on the principal-agent theory, using large-scale survey data including 300 rural junior high schools, 600 mathematics teachers and 33471 sample students to investigate the difference in teaching quality between special and general teachers. At the same time, in order to ensure the validity of the estimation results, this paper not only based on the quasi-experimental research design method, but also conducted multi-dimensional robustness test and heterogeneity analysis on the assessment results. Moreover, based on the non-cognitive skills as the outcome variable, this paper conducted an in-depth discussion on the teaching quality of Specially Contracted Teachers. On this basis, theories and empirical tests were conducted on the results that the teaching quality of Specially Contracted Teachers did not show better results than that of general teachers.

The main research findings of this paper are as follows: First, although the Specially Contracted Teachers are significantly higher than the general teachers, compared with the classes taught by the general teachers, the average grades of the classes taught by the Specially Contracted Teachers are not significantly higher, even the performance is not significantly lower than that of general teachers. Second, this paper further uses non-cognitive ability indicators as dependent variables, and also finds that there is no significant difference in mathematics learning anxiety and learning motivation among students who are taught by special teachers compared to the classes taught by general teachers. Third, heterogeneity analysis shows that, compared with students with better family socioeconomic status, the teaching of special posts will reduce the math performance of students ranked in the bottom 25% of family assets. Fourth, based on the principal-agent theory, the possible mechanism of policy distortion is analyzed, and it is found that the Specially Contracted Teachers are significantly lower in length of extracurricular tutoring than general teachers, and the time and energy for teaching is not as good as that of general teachers. Further, the follow-up investigation found that the loss of Specially Contracted Teachers was serious, and nearly half of the Specially Contracted Teachers flowed into the primary and secondary schools in counties, cities, and it can be speculated that the phenomenon of "find some kind of bridge job first while looking for a nice one." may be widespread among the Specially Contracted Teachers. Because there is no peace of mind to teach in rural areas, it is difficult for Specially Contracted Teachers to focus on improving student performance, so they do not show better quality in teaching, which greatly restricts the implementation of Specially Contracted Teachers policies. This article provides empirical evidence support for further policy revisions.