The proportion of pupils attending state schools in England dropped in the week before half-term amid concerns about the Delta variant of coronavirus, Government figures show.

Around 88% of state school pupils were in class on May 27, down from 91% on May 20, according to the Department for Education (DfE) statistics.

The DfE estimates that approximately 1.8% of all pupils, around 139,000 children, on roll did not attend school for Covid-19 related reasons on May 27, compared to 1.3% the previous week.

But in the North West of England, where there has been an increase in coronavirus cases, around 4% of pupils did not attend school on May 27 for Covid-19 related reasons, according to the DfE analysis.

Nearly a third (31%) of secondary school pupils and more than a fifth (21%) of primary school pupils in Bolton were absent linked to Covid-19 on the week before half-term, the figures suggest.

Overall, across England, the data suggests that 116,000 pupils were out of class and self-isolating on May 27 due to potential contact with a case of coronavirus, compared to 82,000 the previous week.

The figures come after Health Secretary Matt Hancock urged pupils returning to class this week after half-term to get tested to ensure they are not asymptomatically carrying the virus.

School leaders’ unions are calling on the Government to be cautious before any further easing of Covid-19 restrictions and to be proactive to ensure that transmission in schools does not “proceed unchecked”.

On the week before half-term, 90,000 pupils were self-isolating due to a potential contact with a Covid-19 case from inside the school, up from 60,000 on May 20, a rise of 50%.

A further 26,000 pupils were self-isolating due to a possible contact outside school, up from 22,000 the previous week.

Meanwhile, 19,000 pupils were absent because they suspected they had Covid-19, up from 18,000 on May 20, and 4,000 were off after testing positive for Covid-19, the same as the week before.

Around 0.1% of pupils in state schools were absent on May 27 because their school was closed due to Covid-19 related reasons, the analysis shows.

Approximately 82% of secondary school pupils attended on May 27, down from 87% on the previous week, but the DfE estimates that this drop was partially due to schools offering different provision for year 11 and 13 pupils.

In secondary schools, Covid-related absence was 2% on May 27 and in primary schools it was 1.6%.

The South West of England had the lowest levels of Covid-19 related pupil absence of any region, with levels well below 1% throughout the half term, compared to 4% in the North West on May 27.

Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said: “We are clearly now seeing the impact of the Delta variant feeding through into these statistics, and this is reflected by the fact that absence is highest in areas that have been worst affected by the variant.

“This means that many pupils are having to self-isolate in line with Covid protocols and will be experiencing yet more disruption.”

He added: “This situation highlights the fact that the utmost caution is needed in the weeks ahead before any further easing of Covid restrictions, and the current measures must also be kept under review to see if any other actions are immediately required.

“In the longer term, this continued disruption provides yet more evidence of the need for the Government to put forward a much more ambitious education recovery plan than it has so far managed.”

Paul Whiteman, general secretary of school leaders’ union NAHT, said: “We are hearing from our members that more and more schools are having to close multiple classes or ‘bubbles’, particularly in areas with higher case numbers, and revert to remote learning.

“One school told us that though they were not officially closed, six of their seven year groups were isolating due to Covid.”

He added: “The Government must be proactive to ensure that transmission in schools, particularly in relation to the new variant, is not allowed to proceed unchecked.

“We must not sleepwalk into further widespread disruption to education.

“We would urge the Government to do everything necessary to protect school communities.”

Labour’s Peter Kyle, shadow minister for schools, said: “Today’s shocking new data demonstrates the Government once again failing to keep our children learning in school, with those in the North West hit the hardest.

“Over the last year, the Conservatives have ignored Labour’s calls for Covid security measures in schools, from proper testing to Nightingale classrooms, and the resources to make schools Covid secure.

“Now it’s children and families in the North West who are paying the price.”

A Government spokesperson said: “Over 99.9% of schools remain open, with robust protective measures in place – including regular testing and small group bubbles – to keep classrooms open and staff and pupils safe.

“We are also taking additional measures in areas with higher prevalence of the Delta variant, including increasing testing for staff, pupils and families, and keeping face coverings where appropriate.”