Police spokesman Sgt. Aaron Dunbar said the shooter appeared to be a student. He was arrested after the attack at Roseburg High School.
The school went into lockdown after the shots were fired about 7:45 a.m., and administrators were preparing to send students home. The suspect was not immediately identified and no motive for the shooting was disclosed.
A nearby elementary school in Roseburg, a southwest Oregon town of about 21,000 residents, also was locked down as a precaution.