Wage bills for academy managers have soared by almost a third, despite schools facing a funding crisis.
Academy trusts in Suffolk and Essex spent 29% more on salaries for top managers last year compared to 2017, with the total bill topping £18m.
Top-paid chief executives are earning 9% more - with Julian Drinkhall, CEO of Academies Enterprise Trust which runs 62 schools including 10 in north Essex, earning £290-300,000.
Graham White, from the National Education Union, said: "Schools need a management structure but this should not be top heavy or at expense of frontline resources."
Academies said the increased wage bill was due to expansion, requiring extra managers. Some said management spend had decreased when considered as a percentage of the total wage bill.
But the accounts of Orwell Multi-Academy Trust and John Milton Multi-Academy showed a decline in teaching staff, while management positions increased.
OMT, which runs six Suffolk schools, said the reduction of teaching staff from 79 to 73 last year, was due to part time staff being replaced by full time equivalents. The trust spent £670,028 on key management in 2019, up from £462,563.
Trust CEO Anna Hennell James said increased management spend was due to a new school joining and a pay rise for teachers.
John Milton Academy Trust, which runs four Suffolk primary schools, saw teacher numbers fall from 90 to 84 from 2018-19. During that time, management spend increased.
The Trust's CEO Karen Grimes said the extra management spend was due to two posts moving from part time to full time, which provided additional support for improvements, including a new post-16 block at Stowupland site.
She said the number of posts had not been cut - the reduction was due to staff turnover.
Unity Schools Partnership which runs 23 schools, also saw management spend increase and CEO Tim Coulson agreed as much as possible should go on frontline staff and said the increase in management costs was due to employing two extra staff and a national pay rise.
Jack Abbott, Labour's education spokesman at Suffolk County Council, said the rise in senior management pay filled him with "deep unease".
He added: "Every penny possible should be invested in front line staff and resources, pure and simple."
Increases in spending were also reported at Asset Education and The Sigma Trust.
Sigma Trust CEO Jeff Brindle said the increase was due to two large schools joining. He said the proportion of the total wage bill spent on management actually fell between 2018-19.
Asset Education CEO Clare Flintoff, also said the increase in management spending was due to four schools joining.
She said key management spend as a proportion of total staff cots had fallen. "At ASSET we have a clear policy and aim to keep management spend as small as possible and to ensure that our funding is directed to the front line - the classroom," she added.
Academy credits high-earning chief with transforming organisation
The region's top paid academy chief executive received at least £290,000 in a year - despite waiving a pay rise for three years.
Academies Enterprise Trust paid chief executive Julian Drinkall £290-300,000 in 2017/18.
The trust said Mr Drinkall's pay had remained the same for three years, despite improvements across AET.
"Mr Drinkall has transformed the organisation - not only have our schools improved their results in tests, public examinations and Ofsted gradings, but financially the organisation is in far better health," a spokesman added.
"Having previously had year on year deficits reaching £8m pounds, the trust has for the second year running posted a surplus."
REAch2, which runs 51 academies, including eight in Suffolk and nine in Essex, paid its top staff member £230-240,000.
The trust said its CEO's pay was determined by a remuneration committee which took into account the fact REAch2 is the largest primary-only academy trust in the country.
The trust added that the chief executive's salary had remained the same for three years, despite it having grown. However, the chief received £240-250,000 in 2017/18 due to a performance related payment.
Academies expected to ensure maximum investment in classroom
Academy trusts are required to show a "high level of accountability and transparency" in their finances, the Department for Education has said.
A spokesman for the Department for Education also said it had confidence in academies' abilities to manage their budgets "to ensure the maximum possible amount is invested in the classroom".
"Last year we launched our teacher recruitment and retention strategy which aims to support the 450,000 teachers already working in schools in England," the spokesman added.
The Department for Education said it was essential to have the best people leading schools to raise standards, but added that salaries must be justifiable - particularly in cases of significant increases.
It said the Education and Skills Funding Agency had a "robust strategy" to intervene in academy trusts when there is deemed to be a risk to public funds.
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