Larchwood Primary School has taken “necessary precautionary action” to prevent the spread of the variant.
Contact tracing of an omicron case in Brentwood, an Essex town, revealed a link to the school, the local council said on Monday morning.
Specialist testing is being made available to pupils and staff at the primary school in Pilgrims Hatch, according to Essex County Council.
Arrangements have also been made for one class to learn remotely as a preventative measure against the spread of the omicron variant.
It comes after the government tightened Covid measures in school in light of the variant, issuing advice for face masks to be worn in communal areas in secondary schools except for classrooms.
Children – along with adults – also need to isolate for 10 days if they are identified as a close contact of an omicron case.
Announcing the new measures for Larchwood Primary School, the local council tweeted: “We appreciate that this is an unsettling time for parents, pupils and the school community but we take the time to remind everyone that this is a precautionary measure.”
Dr Michael Gogarty, Essex’s top public health official said tests on students at the school have begun, and that testing will continue throughout Monday.
He told BBC Breakfast the infected person was “well” – but did have some symptoms – and isolating with their family.
A total of 11 omicron infections had been recorded in the UK as of Monday.
The variant has an unusual number of mutations. There have been growing concerns it is highly transmissible and could reduce the efficacy of vaccines.
Dr Jenny Harries, head of the UK Health Security Agency, said at the weekend it was “very likely” that further cases of the variant would be discovered in the UK in the coming days.