With an air of confidence, a seventh grader wearing a suit and royal blue tennis shoes recounted the story of how he lost his leg after crawling through a hole in a fence and jumping onto a moving train. The railroad company was at fault, he said on the witness stand, for not building a more secure fence around the tracks.

One of his classmates took the stand shortly after and solemnly explained that her son was injured that day as he walked home, alone, from school because she was working at the time and couldn't pick him up.

These stories were part of the testimony Friday at a mock trial in Washington where nearly 50 middle school students gathered alongside top litigators—actual attorneys—to present cases before two D.C. Superior Court judges.