The boy replied, "Yes," according to the report.
Fuller went to the front office to sign the boy out and put the child in his car with his wife.
WIS reported that Fuller was on an approved list of people who could pick up students, according to the report.
Fuller's wife handed the boy a Happy Meal in the backseat but did not turn around to look at him.
The grandmother noticed they had the wrong boy once the family got home, and the grandparents went back to the school to return the student.
"He had a tooth missing in the front, and I know my grandson did not have a tooth missing in the front," Fuller said. "Immediately, I brought him back to school, and I am very sorry."
"The mother was concerned but relieved that the situation was handled and corrected," the report said. "She admitted that the (grandfather) resembles her father and saw how her son also mistakenly thought he was, indeed, his grandfather."
The boy's father, Darrin Pressley, told WIS he blames the school for making the mistake.
"If they didn't bring him back, my son could've been gone," Pressley said. "It's gross negligence on the school's part. My thing is, you know, have a prevention so this could never happen again."
The school is revising its system for checking students out of school because of the incident. In addition to the summer installation of new entrances that will only allow parents to enter through the front office, students now have to verbally identify the person who is picking them up. The front desk will then double check the person's name from an approved pick-up list.
"He had a tooth missing in the front, and I know my grandson did not have a tooth missing in the front. Immediately, I...Posted by WIS TV on Tuesday, May 31, 2016