CHICAGO (CBS) — Whitney Young Magnet High School will be placed on a “soft lockdown” Wednesday and students will be screened at metal detectors after a threat was scrawled in a bathroom.

An image posted on social media shows a message scratched in one boys’ bathroom, saying “You will all pay 12/5.”

In an email sent to parents, students will go through metal detectors “until further notice. All student possessions are subject to be searched.”

During the soft lockdown on Wednesday, students will not be allowed to go off campus for lunch. Students caught outside the building will be suspended for one day.

Students will also be suspended for one day if they open a door for anyone, including family members, Principal Joyce Kenner said in the email.

There will be an increased police presence on campus.

“I want to first start off by saying thank you to the parents and students who sent us the information about the threat to our school,” Kenner said in the email.

“After a thorough investigation we only found one bathroom (boys) that had the threat to the school. The threat said “You will all pay 12/5.”