About 400 elementary school students are attending school in Sandy Hook for the first time since a shooting rampage there killed 20 first-graders and six educators.
A new 86,000-square-foot school opened Monday in Newtown, Connecticut.
It replaces the one torn down after the 2012 shooting.
The $50 million replacement was built on the same property, but not in the old footprint.
About 70 current Sandy Hook students attended the old school when the shooting occurred.
School officials say about 35 of them were in the building at the time, but none witnessed the shootings.
Those students are now fourth graders.
After the shooting, the students were sent to a school in neighbouring Monroe.
The gunman killed his mother before driving to the school, where he killed himself as police arrived.