Authorities say the suspect, 17-year old Grant Acord, had explosives hidden in the floorboards of his home in West Albany, just over an hour from Portland.
Acord is expected to be charged as an adult in court Tuesday. He faces attempted aggravated murder and other charges. Police were alerted last week when the friend's mother called 9-1-1.
On Tuesday, police and counselors planned to meet with students returning from the holiday weekend.