Alex Woinski, an eighth-grader at West Brook Middle School in Paramus, was sent home from school on Friday because of his costume.
Alex, who has shoulder-length brown hair, wore a white robe, a red sash, sandals, a fake beard and a crown of thorns.
His mother says Alex was told he could keep the costume on if he removed the beard and crown of thorns, but he declined.
Superintendent James Montesano says the district doesn't want students wearing costumes that could be distracting.
The boy's mother is Catholic.