Complex sentence: In 1915, when the film The Birth of a Nation was released, posters advertising it were posted in their neighborhood, and some of the children compared the Matthews children to the racist images on the posters.
Split into simpler sentences: In 1915, when the film The Birth of a Nation was released, advertisements for it were posted in their neighborhood. Some of the children likened the Matthews children to the racist stereotypes depicted on the posters.