In early civilizations, people were educated informally: primarily within the household. As time progressed, education became more structured and formal. Women often had very few rights when education started to become a more important aspect of civilization. Efforts of the ancient Greek and Chinese societies focused primarily on the education of males. In ancient Rome, the availability of education was gradually extended to women, but they were taught separately from men.
The early Christians and medieval Europeans continued this trend, and single-sex schools for the privileged classes prevailed through the Reformation period. In the late 19th and early 20th centuries, coeducation grew much more widely accepted. In Great Britain, Germany, and the Soviet Union, the education of girls and boys in the same classes became an approved practice. In the 16th century, at the Council of Trent, the Roman Catholic church reinforced the establishment of free elementary schools for children of all classes.
The concept of universal elementary education, regardless of sex, had been created.  After the Reformation, coeducation was introduced in western Europe, when certain Protestant groups urged that boys and girls should be taught to read the Bible. The practice became very popular in northern England, Scotland, and colonial New England, where young children, both male and female, attended dame schools. In the late 18th century, girls gradually were admitted to town schools.
The Society of Friends in England, as well as in the United States, pioneered coeducation as they did universal education, and in Quaker settlements in the British colonies, boys and girls commonly attended school together. The new free public elementary, or common schools, which after the American Revolution supplanted church institutions, were almost always coeducational, and by 1900 most public high schools were coeducational as well. 
The early success and achievement of women at Oberlin College persuaded many early women’s rights leaders that coeducation would soon be accepted throughout the country. However, for quite a while, women sometimes suffered uncivil behavior from their male classmates. The prejudice of some male professors proved more unsettling. Many professors had disapproved of the admission of women into their classes, citing studies that stated that women were physically incapable of higher education, and some professors found it difficult to acknowledge women’s presence once they were admitted.
Even today, there have been books, studies, and other arguments claiming that women and men learn very differently from each other because of their brain differences. One of these books is called “Boys and Girls Learn Differently! ” by Michael Gurian.  By the end of the 19th century, 70% of American colleges were coeducational. In the late 20th century, many institutions of higher learning that had been exclusively for people of one sex became coeducational.