Meta has used back-to-school pictures of schoolgirls to advertise one of its social media platforms to a 37-year-old man, in a move parents described as “outrageous” and “upsetting”.

The man noticed that posts encouraging him to “get Threads”, Mark Zuckerberg’s rival to Elon Musk’s [Twitter], were being dropped into his Instagram feed featuring embedded posts of uniformed girls as young as 13 with their faces visible and, in most cases, their names.

The children’s images were used by Meta after their parents had posted them on Instagram to mark their return to school. The parents were unaware that Meta’s settings permitted it to do this. One mother said her account was set to private, but the posts were automatically cross-posting to Threads where they were visible. Another said she posted the picture to a public Instagram account. The posts of their children were highlighted to the stranger as “suggested threads”.

The recipient told the Guardian the posts felt “deliberately provocative and ultimately exploitative of the children and families involved”.