School districts in numerous states are warning about a hack of the Seesaw app.
The Schodack School District in New York informed users that the app is "experiencing a nationwide issue."
Parents and teachers have reported getting links to inappropriate images, the district said.
Seesaw says on its website that more than 10 million teachers, students and family members use its product.
In a statement to NBC News, the company's vice president of marketing said that “specific user accounts were compromised by an outside actor," and the company is working to make sure inappropriate images are not spread further.
In the meantime, parents are encouraged to reach out to teachers directly.