( CNN ) -- The scrolling list of online student activities for Tuesday , April 20 , lists a spring play rehearsal , a talk by `` famous photographer , John Fielder '' -- and `` NO SCHOOL . '' It 's a tough day to be within those walls . It was there , 11 years ago , that Eric Harris and Dylan Klebold embarked on a massacre -- shooting 12 classmates and a teacher dead and injuring 23 others before turning the gun on themselves . Columbine High School was forever etched into the psyche of America . The top news story of 1999 . An iconic shooting . An event prompted intense debate over gun control . `` A day that changed us forever , '' as former President Bill Clinton said at 10th anniversary observances last year . Clinton , who was in the White House at the time of the killings , said he was personally inspired by the courage of the Columbine community . Tuesday marks anniversary number 11 , an odd-year milestone that millions of Americans will let come and go without notice . But for the survivors , for the victims ' families and friends , time 's steady march is not enough to dull the pain . The memories are still raw in Littleton , Colorado . Principal Frank DeAngelis attended a teary prom last weekend when Columbine crowned a king and queen with special needs . An act of goodwill and fraternity . An act exemplifying the human spirit . `` This , '' DeAngelis told CNN affiliate KMGH in Denver , is what Columbine is all about . '' In far away Dallas , Texas , Jordan Niland , 17 , said he is sure to pick up his telephone Tuesday . He will dial the number of Richard Castaldo . Castaldo , a junior at Columbine in 1999 , suffered five gunshot wounds to his chest , back , arm and colon that left him paralyzed from the waist down . Niland was a young boy then . But after seeing Michael Moore 's documentary , `` Bowling for Columbine , '' he struck up a MySpace conversation with Castaldo . The two have been friends since . '' `` The anniversary means so much to me , '' Niland said . `` I have had the privilege to talk and get to know a survivor and to fully understand what really went on that day . '' If people could personally hear Castaldo 's story , Niland said , they would stop to reflect on this day . Because such a horror , he said , should not be forgotten . And because life goes on . A Columbine memorial dedicated in 2007 , is sure to be visited Tuesday . But like the tragedy itself , the memorial , meant as a place of reflection , is incomplete , gaps running through it like the voids in people 's lives . The memorial park has posted a wish list to complete the peace it is intended to bestow . Hackberry trees , lavender mist , spirea , purple asters . And 24 columbines . Any variety will do , the memorial 's website says . As long as they are columbines .
Columbine High School will be closed on day of anniversary . `` Day that changed us forever , '' former President Bill Clinton said last year . Memorial park has posted a wish list of items sought to complete it .