School districts that were affected by a PowerSchool data hack in December are now facing extortion attempts by cyber criminals, according to the K-12 ed-tech company.

Months after the hacked education software maker PowerSchool paid a hacker’s ransom to delete the company’s banks of stolen student data, at least one school district says it is now being extorted by someone who said the data was not destroyed.

Software maker said it paid its attackers even as the true size of the theft is still unknown.