Mixed-sex education, also known as mixed-gender education, co-education, or coeducation (abbreviated to co-ed or coed), is a system of education where males and females are educated together. Whereas single-sex education was more common up to the 19th century, mixed-sex education has since become standard in many cultures, particularly in Western countries. Single-sex education, however, remains prevalent in many Muslim countries. The relative merits of both systems have been the subject of debate.
The world's oldest co-educational school is thought to be Archbishop Tenison's Church of England High School, Croydon, established in 1714 in the United Kingdom, which admitted boys and girls from its opening onwards. This has always been a day school only.
The world's oldest co-educational both day and boarding school is Dollar Academy, a junior and senior school for males and females from ages 5 to 18 in Scotland, United Kingdom. From its opening in 1818, the school admitted both boys and girls of the parish of Dollar and the surrounding area. The school continues in existence to the present day with around 1,250 pupils.
The first co-educational college to be founded was Oberlin Collegiate Institute in Oberlin, Ohio. It opened on 3 December 1833, with 44 students, including 29 men and 15 women. Fully equal status for women did not arrive until 1837, and the first three women to graduate with bachelor's degrees did so in 1840. By the late 20th century, many institutions of higher learning that had been exclusively for people of one sex had become coeducational.