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.

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

Wheeler was arrested on the child porn charges 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.