Some 50 elementary school children witnessed a brutal murder on their way to school in a suburb of a large city

Statistics Nov 11, 2020

Some 50 elementary school children witnessed a brutal murder on their way to school in a suburb of a large city. The school officials worked with a social worker, a school psychologist, and others in an attempt to help the children deal with their emotions, to avoid long-term ill effects, and to help parents with their children. A year after the tragedy, there appeared to be no serious aftereffects. What assumptions are necessary to claim that those efforts were useful?