19世纪70年代到20世纪20年代是美国现代大学崛起的时期，也是美国女子高等教育从边缘走向主流的时期，其中男女同校学院和大学是女子接受高等教育的主导机构，但已有研究却更加关注女子学院。本研究结合社会性别理论和方法，以密歇根大学、康奈尔大学、哈佛-拉德克里夫学院和弗吉尼亚大学等高校为个案，探讨了男女同校从内战前后的试验期、镀金时代的形成期到进步时代的曲折前进期的历史变迁，以及这种变化如何从课程教学与学院生活两大方面形塑男女学生之间的社会性别关系。

内战前后，在乡村学园的男女同校传统、西进运动和福音派狂热运动中，男女同校得以在西部和中西部的小型教派学院和少量州立大学扩散，这些学院和大学往往模仿奥柏林学院实施“有限的男女同校”模式，在课程学习、宗教礼拜和就餐中男女融合，但是在手工劳动中采取家庭式性别劳动分工，并且明确规定学院生活中男女分离。整体而言，男女同校尚未提上日程，男女学生仍然处于分离领域观念和实践的禁锢和束缚之中。

1870-1890年是大学男女同校的形成期，高等教育界从女性身体/生理、智力和道德三个方面对男女同校展开了辩论，在实践中出现了以密歇根大学和康奈尔大学为代表的完全男女同校、以哈佛-拉德克里夫学院为代表的附属制男女同校两种类型，前者在入学标准、课程教学、学业评价和毕业考试等方面赋予女性平等权利，后者事实上成了女子学院，女学生虽然与男学生享有同样的入学标准，却在教育过程和毕业证书方面完全不对等。在这两类男女同校院校中，男女学生之间的社会性别关系复杂多变，既有相对自由放任的互动，也有从自由走向隔离的保守转向，以及更彻底的男女完全隔离。

1890-1920年男女同校在曲折中前进，在成为高等院校的主流教育形式的同时出现了短暂挫折和局部滞后。女学生涌入带来的性别焦虑、对第二代女学生缺乏严肃目的认知以及大学扩张和转型中高校管理者对新学生管理方案的需求是其曲折发展的重要原因。男女同校的曲折发展的重要体现是高校从制度层面确保男学生的优势地位，然而，在学院生活中，女学生逐步通过单一性别的学生组织巩固其在校内的地位。吊诡的是，单一性别学生组织表面看强化了性别分离，但是男女学生通过这些组织展开的互动却孕育了更加平等的性别关系。此外，男女同校的滞后尤其体现南部的弗吉尼亚大学，该校直到20世纪七十年代才实现本科层次的男女同校。

研究发现，男女同校的历史变迁是女性打破社会性别分离的界限，从高等教育的外围走向中心的过程，也是逐步获得平等受教育权的过程。保守与进步势力的同步发展构成了男女同校发展的重要特征，也正是这一矛盾体导致了男女同校发展的曲折反复，推动了社会性别关系从分离到平等的演变。一方面，校方通过将分离领域的观念融入对女学生的正式管理、学院生活中的非正式文化等方式再生产了旧有的社会性别关系。另一方面，男女学生通过女学生组织和男学生组织之间的互动塑造了更加平等的性别关系，其中,女学生性别角色的转变在这一关系中至关重要。男女同校的历史变迁是美国现代大学崛起的重要内容，对于美国高等教育的学科结构、学生管理、女子教育以及美国社会和文化的变革都具有重要意义。

The period from the 1870s to the 1920s was a time of the rise of the modern American university and a time when women's higher education in the United States moved from the margins to the mainstream, with coeducational colleges and universities being the leading institutions of higher education for women, but previous studies had focused more on women's colleges. Drawing on gender theory and methodology, this study examines the historical changes of the coeducation system from the experimental period around the Civil War, the formative period of the Gilded Age to the tortuous forward period of the Progressive Era, and how such changes shaped the gender relations between male and female students from two major aspects of curriculum &teaching and college life, using the University of Michigan, Cornell University, Harvard-Radcliffe College, and the University of Virginia as cases.

Around the time of the Civil War, the coeducational traditions of rural academies and seminaries, the Westward movement, and evangelical fervor allowed for the proliferation of coeducation at small denominational colleges and a handful of state universities in the West and Midwest, which often emulated Oberlin College's "limited coeducation" model of integrating male and female students in course work, religious worship, and dining, but with a family-style gender division of labor in manual work and a clear separation of the sexes in college life. In general, coeducation was not on the agenda of higher education at that time, and students confined and bounded by the notion and practice of separation spheres.

1870-1890 was the formative period of the coeducation system in universities. The coeducation system was debated in higher education circles from three aspects: women physical/physiological, intellectual and moral, and two types of coeducation emerged in practice: the fully coeducational system represented by the University of Michigan and Cornell University, and the coordinate colleges represented by Harvard-Radcliffe College. The former gave women equal rights in terms of admission criteria, curriculum, academic evaluation and graduation exams, while the latter had become a de facto women's college, where female students enjoyed the same admission criteria as male students, but were not equal in terms of educational process and graduation certificates. In both types of coeducational institutions, gender relations between students were complex and variable, ranging from relatively laissez-faire interactions to a conservative turn from freedom to segregation and, more radically, complete segregation of the sexes.

The coeducational system during1890-1920 moved forward in a tortuous manner, with brief setbacks and partial lags as it became the dominant form of education in institutions of higher learning. Gender anxiety brought about by the influx of women students, the lack of serious purpose of second-generation women students, and the need for new student management programs by college administrators in the midst of university expansion and transition were important reasons for its tortuous development. An important manifestation of the convoluted development of coeducation was that colleges and universities ensure the dominance of man students at the institutional level, yet women students gradually consolidated their position on campus through single-sex student organizations in college life. Paradoxically, while single-sex student organizations ostensibly reinforced gender separation, the interactions between male and female students through these organizations had fostered more egalitarian gender relations. Moreover, the lag in coeducation was particularly evident at the University of Virginia in the South, where coeducation at the undergraduate level did not occur until the 1970s.

The study found that the historical transformation of coeducation was a process of breaking the boundaries of gender separation in society and moving from the periphery to the center of higher education for women, as well as a process of gradually gaining equal rights of education. The simultaneous development of conservative and progressive forces constituted an important feature of the development of coeducation, and it was this contradictory body that has led to the tortuous iterations of coeducation and promoted the evolution of gender relations from separation to equality. On the one hand, the school authorities reproduced the old gender relations through the integration of the idea of separate spheres into the formal management of female students and the informal culture of college life. On the other hand, male and female students had shaped more egalitarian gender relations through the interaction between female and male student organizations, in which the transformation of female students' gender roles had been crucial. The historical transformation of coeducation was an important element in the rise of the modern American university and had implications for the disciplinary structure and student governance of American higher education, women's education, and the transformation of American society and culture.