Mold has been reported in seven schools across New Jersey, including Hopatcong.
Students there will now return to school on Sept. 10.
The date was pushed back after mold was found at Hudson Maxim and Tulsa Trail Elementary schools.
According to administrators, all rooms are being tested to determine the extent of the mold growth and what remediation efforts, if any, are needed.
Dehumidifiers were also brought into both schools.
Other schools reporting mold across the state include Emma Havens Young Elementary School
and Lake Riviera Middle School in Brick Township, McKinley Avenue Elementary School in Stafford Township, White Township School and Lakehurst Elementary School.