Principal James Riccobono will offer words of encouragement during an address to all 2,900 students before classes begin Monday.
Counselors also are on hand.
Authorities say a 16-year-old junior was arrested Thursday after a police resource officer at the school was told the teen was planning an attack.
Authorities say they found shotgun shells, bullets, black powder and explosive devices in the teen's home.
Officials also arrested a 17-year-old Immaculata High School senior, who is a competitive target shooter.