The man who set fire to a Roberts school pleaded guilty to a charge of arson Friday in St. Croix County Circuit Court, and seven other charges against him were dropped, according to court records. Justin Walter Nelson, 25, of Roberts, started a fire at St. Croix Central Elementary School after breaking into the building in the early morning hours of April 30 in an apparent burglary attempt. After pleading guilty to the arson charge, charges of burglary, criminal damage to property and possession of THC were dismissed. Four charges against Nelson from an April 18 incident were also dropped but will be used as read-ins in sentencing.