A video posted online shows students at John Mall High School in Walsenburg making an emotional plea for a missing classmate to come home.
The Huerfano County Sheriff's Office says that Shanelle Bobian, 17, hasn't been seen or heard from since August 22.
Bobian was initially reported as a possible runaway, but now she is listed as a missing person.
Bobian is 4-feet-10-inches tall and weighs 95 pounds. She has brown hair and brown eyes.
Anyone with information about Bobian's whereabouts is asked to call 719-738-1600.