Wider context
Schools in Scotland and Northern Ireland received threats on Wednesday, too. It is unclear whether the incidents are connected.
On Thursday morning, a bomb alert at a Calais rail station delayed international and national train services in northern France.
The latest incidents follow a series of bomb hoaxes last week against airports and airlines in a number of European countries. Although a number of threats were claimed by an extremist misogynistic group, it later denied any link to the false warnings.
Many parents have been demanding clarity and action from the government. La Repubblica newspaper reports that protests have been held against a decision by the headmaster of a secondary school in Rome who did not take any action, saying she had realised the threatening message to contain typos and therefore be "fake". According to the newspaper, protesters want new national guidelines to be issued.