Four-year-old AJ Whylly was among the children who made a school trip from Marshall, Minn., to the Children's Museum of South Dakota on Tuesday, but he was not on the bus for the return trip, KARE 11 reports.
Teachers did not realize that the boy, who has a speech delay and difficulty communicating, was not among them until they got back to the southwestern Minnesota school, more than an hour's drive from the museum in Brookings, S.D.
The boy was safely reunited with his mother, but she was angered that her boy was left alone.
"It's the worst nightmare I could have ever been in," the boy's mother Jacqueline Whylly told KARE 11.
Superintendent Klint Willert apologized and said a second count of children once they were on the bus was not taken, and disciplinary action against a teacher is being taken. A meeting of district administrators was scheduled for Thursday morning to review field trip procedures.