Bomb-sniffing dogs checked the hallways and classrooms at Chesterfield High School, authorities said. Metal detectors were borrowed from a courthouse, and police met students at the doors.
The father of one 16-year-old sophomore said the police work over the weekend gave him confidence his son was safe.
"I think they're pretty much on top of it. They've had plenty of time to find anything," said parent Michael Wattson.
The suspect, Ryan Schallenberger, 18, was assigned a lawyer during a brief court hearing Monday. The teen was silent but appeared agitated, his eyes widening at the sight of cameras awaiting him when he entered, hands cuffed and ankles shackled.
Mr. Schallenberger was arrested Saturday after his parents called police because the teen had ordered 10 pounds of ammonium nitrate, which they had retrieved after getting a delivery notice from the postal service, authorities said Monday. Police also said they discovered a disturbing journal.
Chesterfield County prosecutor Jay Hodge said he will ask that the teen undergo a mental evaluation when he appears in court today for a bail hearing.
Police Chief Randall Lear said Mr. Schallenberger "seemed to hate the world. He hated people different from him -- the rich boys with good-looking girlfriends."
Mr. Schallenberger was one of the top students at the high school of about 544 students and had not caused any serious problems, Principal Scott Radkin said.
The school's Web site lists Mr. Schallenberger as a member of the 2007 academic bowl squad. He won an academic award from Newberry College last year.
The teen was in the Chesterfield County jail Sunday night, charged with possessing materials to make bombs, the police chief said. No other weapons were found at his home, he said.
Mr. Schallenberger kept a journal for more than a year that detailed his plans for a suicide attack and included maps of the school, police said. The writings didn't include a specific time or the intended targets.
The teen planned to make several bombs and had the supplies needed to kill dozens, depending on where the devices were placed and whether they included shrapnel, Chief Lear said. Ammonium nitrate was used in the Oklahoma City bombing in 1995, which killed 168 people.
Mr. Schallenberger also left an audio tape that was to be played after he died explaining why he wanted to bomb his school, authorities said. Chief Lear wouldn't detail what was on the tape except to say Mr. Schallenberger was an angry young man.