In Sunderland, the busiest secondary school was Southmoor Academy, which had 1,264 school places but 1,408 children on its roll – meaning it was 11 per cent over its official capacity.
This was followed by St Anthony's Girls' Catholic Academy, seven per cent over capacity, and Biddick Academy, six per cent over capacity.
Education leaders at Southmoor Academy cited a high demand for places along with successful admission appeals which led to subsequent awarding of additional places as a reason for the figures and also moved to reassure parents over class sizes.
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A statement from the school said: “Southmoor has been oversubscribed for a number of years as a result of very high demand for places from parents and many successful admissions appeals. This is because of the school's long held reputation for providing high quality education, its excellent sixth form and a commitment to providing a strong enrichment programme.
“Managing very high numbers of students in a limited space is a challenge for timetable purposes, however class sizes are in line with national averages as our staffing profile has been carefully matched to meet the growth in student numbers.”
It was a similar message from Executive Head at St Anthony’s Girls’ Catholic Academy, Francesca Craik, who said: “We do our best to accommodate pupils who want to attend our outstanding school.
"In specific circumstances, such as a high birth rate year, we agree arrangements with the local council to provide additional places as necessary to support the education of young people in our area. Our pupil-staff ratios are in line with Department for Education (DfE) guidance.
"We maintain our class sizes to ensure sufficient support and delivery of first-class education for every pupil.”
The City Council also cited successful appeals and the autonomy of academy trusts to make decisions based on assessments of their own resources.
A Council statement said: “Sunderland currently has sufficient capacity across the primary and secondary sector to accommodate all pupils without requiring any school to admit in excess of its Pupil Admission Number.
“Places are offered though the admission process to reflect this. Any admission above a school’s capacity is a result of either a successful appeal or where a school or academy has taken the decision to admit above its own admission number to reflect either unused resources or physical capacity across its site.
“The Council has not, except in unique individual cases, requested a school exceeds its admission numbers nor is there currently a requirement for one to do so.”
In 2018-19 – the most recent comparable year due to coronavirus pandemic restrictions – DfE figures showed five schools in the city were operating at or above their official capacity.
Sunderland’s situation reflects the national picture, with DfE data showing 22 per cent of secondary schools reached their capacity threshold last year – up from 17 per cent in 2018-19, and the highest proportion in a decade.
The Association of School and College Leaders (ASCL) said the rate is driven by increased demand for secondary places, compounded by "perceptions linked to Ofsted reports" which have created an imbalance in demand for places at certain schools.
Geoff Barton, General Secretary of the ASCL, said: “The increasing demand for secondary places is complicated by perceptions linked to Ofsted reports with higher-rated schools often heavily oversubscribed and significant spare capacity at lower-rated schools.
The data shows a very different picture for the country’s and city’s primary schools.
Just 17 per cent of English primaries were at or over capacity last year, the lowest rate since records began in 2009-10.
This included 10 in Sunderland – down from 15 in 2018-19.
The Echo also contacted Biddick Academy but they have not responded.