Unknown to Va. Tech, Cho Had a Disorder

"We don't send anything that has to do with special education," Crowley said. "If the parent, who has the authority, wants us to disclose to colleges that the student was in a special-ed program, we can do that and send whatever records they want. But that doesn't happen very often."

The reason, explained Barmak Nassirian, with the American Association of Collegiate Registrars and Admissions Officers, is that in the competitive admissions process, students don't want to be at a disadvantage. As recently as 2003, parental pressure caused the College Board to stop flagging SAT scores for students who had been given special education accommodations while taking the test.

Moreover, many colleges say they don't want to know because of the potential liability. "In soliciting a student's history of psychiatric treatment or diagnoses by treating physicians, you basically open a Pandora's box," Nassirian said. "Even if you should decide, for reasons that have nothing to do with medical circumstances, not to accept a student, you most certainly will have a case that will be litigated."

For students who are accepted and disclose their disability, most colleges and universities have services to provide appropriate accommodations, said Andrew Flagel, dean of admissions at George Mason University.

Schum said selective mutism, which can be treated successfully, had never been associated with violent behavior. Most of the children, teens and young adults who suffer from the disorder -- about 1 percent of the U.S. population -- are simply born that way. They come from families where anxieties tend to run high.

One technique Schum said he has found particularly effective in helping children overcome their mutism is videotaping. Children can be videotaped reading aloud at home and then can take the tape to their teacher to be graded. Or the student can be videotaped giving a show-and-tell presentation to share with the class.

So Schum was not at all surprised when the world finally heard Cho speak in a setting of his choosing, on the strange and violent tape he sent to NBC News. "He was not autistic. He clearly had the capability of talking to people," Schum said. "We saw that on the video."

Staff writer Sari Horwitz and staff researchers Magda Jean-Louis and Meg Smith contributed to this report.