Cybercriminals demanded ransom payments from school districts nationwide this week, using millions of K-12 students’ sensitive data as leverage after the files were stolen from education technology giant PowerSchool in a massive cyberattack late last year.

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.