CHICAGO (CBS) — Officials with Chicago Public Schools are apologizing for what they said is a data breach exposing private information belonging to thousands of CPS families.

The officials said an employee emailed private student information to more than 3,700 families.

It included names, email addresses, phone and student identification numbers.

The families had all been invited to submit supplemental applications to selective enrollment schools.

They were told that their information was compromised.

CPS officials are calling the error unacceptable and said the employee who sent the email will be fired.