Columbine students Eric Harris and Dylan Klebold shot and killed 12 students and a teacher before taking their own lives on April 20, 1999.
The big event commemorating this anniversary will next weekend's groundbreaking for a $1½ million memorial site in the park next to Columbine, reports CBS News correspondent Lee Frank (audio).
Don Fleming, whose daughter Kelly was killed, says the memorial is a tribute "so that Columbine isn't just remembered for two kids that shot up a school, but that it's also remembered for a community that came together and built a memorial afterwards."
About $500,000 is still needed.
Fleming and a few other parents of Columbine victims are gathering for a private, quiet day of remembrance.
When classes resume Friday, "I'll talk to students about not taking anything for granted, about making wise choices. You know, we had 13 students who did not have a choice. Their lives were taken from them unexpectedly," Columbine principal Frank DeAngelis told Frank.
As a sophomore at Columbine High School seven years ago, Marjorie Lindholm was a cheerleader with a 3-plus grade-point average who wanted to become a doctor.
Her life changed dramatically when the killing spree began on April 20, 1999. Lindholm found herself locked in a classroom with other students and a teacher, Dave Sanders. She was there for four hours as Sanders and 12 classmates were gunned down by students Eric Harris and Dylan Klebold, who shot and killed themselves.
Now 24, Lindholm believes she has only recently begun to heal. Writing a book, "A Columbine Survivor's Story," with her mother has helped, she said.
Many survivors have moved on after the deadliest school shooting in the nation's history. But for other, it has been more difficult.
Sean Graves was shot four times and paralyzed from the waist down. The father of Mark Taylor, who was hit by more than a dozen bullets, left his family in 2001 after 34 years of marriage. Anne Marie Hochhalter's mother killed herself 18 months after the massacre, which left her daughter paralyzed from the waist down.