Pupils from disadvantaged backgrounds in Peterborough are two years behind their peers by the time they finish their GCSEs - the widest gap in England.
A report by the Education Policy Institute (EPI) found that pupils on free school meals in the city were, on average, 24 months behind their peers at the end of secondary school, a measure they call the ‘disadvantage gap’.
Only four other local authorities reported the maximum two-year gap, with the average in the country being 18 months.
In Westminster, poorer GCSE students are just four months behind.
Cllr Lynne Ayres, cabinet member for education at Peterborough City Council, said: “We are concerned about the data in the 2019 EPI Annual Report and will continue to work in partnership with all schools, both maintained and academies, to improve prospects for pupils from disadvantaged backgrounds.
“As we have previously stated, our schools are facing significant funding challenges which are impacting upon all pupils, so we will continue to lobby central government hard for a fairer funding deal.
“One of the reasons we are committed to building an independent university in the city is to increase the chances of young people locally, especially those from a disadvantaged background, going on to higher education.
“We also have the University Technical College delivering courses for young people from Year 10, as well as a range of city employers providing work-based training such as apprenticeships.”
In Peterborough, almost 30 per cent of secondary school pupils are eligible for free school meals - and around one in 10 have been eligible for most of their time in school.
Meanwhile, new Department for Education data shows that Peterborough’s schools excluded pupils 110 times for assaulting adults in 2017/18, a substantial rise from 71 the previous year.
Of these, 107 were temporary exclusions and three were permanent.
Physical assault can mean a pupil wounding, obstructing and jostling, or behaving violently towards an adult.
Dr Mary Bousted, joint general secretary of the National Education Union, said teachers often cite pupil behaviour as a reason why they walk away from the profession.
She added: “All schools should have a policy for dealing with violent incidents and a pupil behaviour policy where teachers feel genuinely supported by school management.
“Cuts to school and local authority budgets, however, mean many support services such as behavioural specialists, who used to help in schools, have gone.”