Southwark Elementary in South Philadelphia will close for several weeks.
Parents were allowed to grab their children's personal belongings on Friday morning.
The school's principal sent a letter to parents saying the dust that may contain asbestos was found.
He says that students and staff should plan to be virtual at the start of next week.
This is the first school in Philadelphia to close this school year due to asbestos concerns.
Six schools were closed at various points last school year due to asbestos issues.