Raiders struck over the weekend and left the building unsafe for pupils after high winds caused further damage to the roof.
Head teacher at the Burton Borough School in Newport, David Hill, said the school would reopen today.
He said: “During the weekend thieves attempted to remove metal from the roof above the School Hall.
“High winds on Sunday night made the situation worse, and when our site team arrived early Monday morning the damage was considerable.
“With high winds, debris being blown around the site, no secure fencing available, and uncertainty as to how many rooms were affected I decided that the only possibility was to close the school.”