About 400 students have returned to Sandy Hook Elementary School for the first time since a shooting rampage there killed 20 first-graders and six teachers.
A new 86,000-square-foot (7,990 square meter) school opened Monday in Newtown, Connecticut.
It replaces the one torn down after the 2012 shooting.
The $US50 million ($A66 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.
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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.
