II.The Reasons behind the U.S. Social Movements in Post-WWII Black and white workers worked side by side during WWII,yet black children still had to attend segregated schools in the South. UNITED WE WINII. The Reasons behind the U.S. Social Movements in Post-WWII Black and white workers worked side by side during WWII, yet black children still had to attend segregated schools in the South