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.

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

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

They were told that their information was compromised.

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