The Duston School, which has 1,650 pupils said it would have to close its doors at short notice.
The academy teaches children aged four to 18, across primary, secondary and sixth form areas.
Parents were emailed on Tuesday evening by headteacher Sam Strickland informing them that the school would close the next day and students would be provided with work to do at home due to the suspected spider infestation.
False widow spiders are sometimes confused for black widows and they are mistakenly thought to be as dangerous as both have similar dark-coloured, round bodies, according to the Natural History Museum.
Bites have meant hospital treatment for some people who believed they were bitten by the species.
The closure comes just weeks after the start of the new school term and has left parents struggling again after the months of home schooling families endured during the pandemic lockdowns.
The statement from the headteacher said: “Please be advised that due to a suspected outbreak of False Black Widow Spiders we are regrettably having to close both phases of the school to all pupils and staff tomorrow (Wednesday 29th September) to allow the situation to be assessed and for the school to be cleaned.”
On Facebook, Lorri-Ann Gillies wrote: “Back to back meetings all day and a pitch at 11am. I mean it’s not as if I wasn’t juggling enough anyway.”
Kirsty Huizinga said it was a ‘nightmare’.
Sunjit Sall added: ‘This country has gone bonkers. Official.’
And Keith Charles branded it ‘snowflakes society’.
The false black widow is one of the the largest invasive species of spider and is found across the Americas, Asia and Europe.
Of six sub-species, three can be found in the UK - mainly in the south of England.
The noble false widow is the most commonly reported subspecies in the UK, where it first appeared in 1879. Originating from the Canary Islands and Madeira, it is believed to have arrived along with imported bananas.
Now firmly established in parts of the country, its exact numbers are not known but are thought to be growing due to increasingly warmer weather - leading to a surge in attacks. In June, researchers at the University of Galway found there were 24 confirmed incidents of false widow bites in scientific literature.