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.

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

PowerSchool is warning that the hacker behind its December cyberattack is now individually extorting schools, threatening to release the previously stolen student and teacher data if a ransom is not paid.