The email, sent at 12:51 p.m. said all students, faculty and staff were evacuated from Francis W. Parker School in Lincoln Park "out of an abundance of caution" after an "unsubstantiated" threat was made to the campus.
The school's security team indicated that the threat came from outside the United States, the email said.
School officials asked parents and guardians to pick up their children nearby.
"Nothing is more important than the safety of our community, and we take every precaution to protect them. We regret this unfortunate disruption," the email said, in part.
The school will be open and holding classes on Tuesday.