Three of the 12 students gunned down at the school April 20, 1999, would have been among the Class of 2000: Cassie Bernall, Corey DePooter and Rachel Scott.
Saturday's commencement ceremony, in which 435 students received degrees, was closed to the public at the request of students and teachers. Most students declined to comment as they entered an amphitheater south of Denver for the ceremony.
"Man, there were a couple of good times. But I'm just glad it's over," graduate Richard Castaldo said before the ceremony. He was hit eight times during the attack and left paralyzed.
Also among the graduates were Pat Ireland, whose rescue from a window of the school library became one of the most enduring images of the attack, and Anne-Marie Hochhalter, also paralyzed.
"I feel like it's a big accomplishment that I'm even able to accept my diploma because I came so close to not being here," Hochhalter told The Denver Post.
Other tragedies have followed at Columbine since the worst high school shooting in U.S. history.
Hochhalter's mother committed suicide in October by walking into a pawn shop, asking for a gun, loading it and shooting herself. Relatives said that she suffered from depression and that the massacre and her daughter's grave injuries were more than she could handle.
In February, Columbine sweethearts Nicholas Kunselman, 15, and Stephanie Hart Grizzell, 16, were shot to death in a sandwich shop near the school. The case remains unsolved.
A week after the anniversary of the attack, Columbine basketball star Greg Barnes hanged himself. Barnes had seen the fatal shooting of teacher Dave Sanders and lost a friend, Matthew Kechter, in the school rampage.
In a statement, Mark and Judy Barnes said their son was depressed by the end of basketball season and the anniversary of the rampage.
"Please make every effort to reach out through family, friends or counsel to release and seek to heal any deep underlying feelings," they said. "No teen-ager should ever have to witness the level of destruction and distress that Greg was exposed to.
"This community doesn't need any more Columbine victims we have all suffered enough."
Written by Robert Weller