The teaching of girls and boys together in the same school and the same class. Whereas primary education has generally always been co‐educational (although up to the 1950s there were often separate entrance doors for boys and girls), it was often the case in the first two‐thirds of the 20th century that boys and girls would attend separate schools for their secondary education. Since the Education Act 1944 (Butler Act) the trend has been towards co‐educational secondary provision. Some researchers suggest that boys achieve better in mixed (co‐educational) classes, while girls may achieve more highly, particularly in science subjects, in single‐sex schools. See also gender.