BRIDGEWATER (CBS) – The Bridgewater-Raynham Regional School District is apologizing for a controversial photo that appears to show a young African-American girl tied to two leashes.

Plimoth Plantation presented a lesson about the Pilgrims to third graders last Friday at the Mitchell Elementary School in Bridgewater.

Administrators said part of that lesson focused on outfits from the 17th century, particularly those worn by parents and children. Some of the children dressed up and posed for a photo with an adult in costume.

The photo showed the adult, a white woman, with her arms around two white children who were holding what appear to be leashes, which were attached to a young African-American girl who is kneeling on the floor in front of them.

The teacher shared the photo with parents of her students and that led to several irate postings of the picture on social media.

Superintendent Derek Swenson said he got word of the complaints late Wednesday and began an investigation early Thursday.

What appeared to be leashes were actually “tethering straps” the superintendent said in a statement, noting that the “garment worn by toddlers commonly used tethering straps to assist them when learning to walk.”

“We realize without this context added to the photo that was shared by the classroom teacher it could be perceived differently,” Swenson said in the statement issued Thursday.

“Please note it was never the intent of the lesson to demean or degrade any one person or group. The Bridgewater-Raynham Regional School District sincerely apologizes to the students, staff and community at large for this unfortunate incident.”