WILMINGTON, Del. — A judge has convicted a former headmaster of an elite Delaware prep school on all 25 counts of dealing in child pornography.

The judge’s ruling Monday came after a trial for 54-year-old Christopher Wheeler. Wheeler was a former headmaster at Tower Hill school, which was founded by members of the du Pont family.

Its graduates include DuPont Co. CEO Ellen Kullman and U.S. Sen. Chris Coons.

Wheeler’s sentencing is tentatively set for March 27. Each of the 25 counts carries a minimum two-year prison term.

Wheeler was arrested after police, prompted by allegations of child sexual abuse, searched his home and office at Tower Hill. He has not been charged in that case.