In the early 20th century, the mind was viewed as a muscle that could be strengthened through mental exercise. Since exercise could be done at home, homework was viewed favorably. During the 1940s, schools began shifting their emphasis from memorization to problem solving. Homework fell out of favor because it was closely associated with the repetition of material. In the 1950s, Americans worried that education lacked rigor and left children unprepared for the new technologies, such as computers. Homework, it was believed, could speed up learning.
In the 1960s, educators and parents became concerned that homework was crowding out social experience, outdoor recreation and creative activities. Two decades later, in the 1980s, homework again came back into favor as it came to be viewed as one way to stem a rising tide of mediocrity in American education. The push for more homework continued into the 1990s, fueled by rising academic standards.
http://www.ed.gov/parents/academic/involve/homework/part.html
