Science teacher Olivia Johntry lost her father, Anthony Perez, on Sept. 11, 2001. Johntry now uses her story as a model of perseverance for her students to carry with them. Courtesy of the 9/11 Memorial & Museum. Watch a special tribute honoring 9/11 victims, survivors and heroes, ending with the iconic "Tribute in Light," live on ABC tonight at 8 p.m. ET. ▻