(Vernonia, OR)  --  Officials say schools in Vernonia will be in lockout mode today, following a potentially credible threat of violence.  Superintendent Aaron Miller says lockout means students will continue in classes as normal, but all doors will be locked and no one will be allowed to enter or leave the school buildings.  KOIN-TV reports police will also present in the schools.  The Vernonia district has four schools, including two elementary, one middle, and one high school.