... As more and more students went to college, more and more went out into the world with new standards of dress. It is important to note that the number of college students grew tenfold in the first half of the 20th century.
Q: What types of obstacles or pushback did students experience from college leaders?
A: College leaders were far more interested in policing the activities of women and, in the 1940s, they developed elaborate dress codes as to when and where particular garments could be worn. Before that, dress codes were enforced by peer pressure or one-on-one interaction with the administrators. So, it was not until jeans, pants, and shorts on women that there was a need for written rules. More than downright outlawing garments, administrators controlled the parameters of when the clothes could be worn. The cafeteria was a highly contested space. For men, they were pushed to wear sport coats and ties, but many protested these rules or simply did not comply. There were very few repercussions for men; women were given demerits or grounded to campus for breaking dress codes. Of course, so much of this enforcement depended on the inclinations of school administrators.
That's from this interview, Deirdre Clemente, the author of Dress Casual: How College Students Redefined American Style.