During this time period teenage fashion in America started to expand. An economic happened. Because of this economic boom there was more money in America. Teens were spending all this money. During these years the "flapper" became very popular and used a lot.
When flappers came out America was shocked. They thought teens were losing their minds when in reality they weren't. They were becoming more confident to dance and have fun in parties.
Fashion changed over time because teens in these times had a lot more money to spend on clothing and to make more styles.