A private tuition company has struck a deal worth about #163;200,000 to teach English and maths lessons in five state secondaries in East Anglia.
The firm will offer one-to-one and group sessions at five "learning centres" at the schools in what is believed to be the first arrangement of its kind.
The schools have agreed to pay #163;22 for each 80-minute lesson the company delivers to its pupils. Parents of pupils from other schools can pay #163;27 to have their children attend the same sessions.
The tutorials will be offered to children who are in need of catch-up lessons and students preparing for their GCSEs at the Samuel Ward Academy and Wymondham High School in Suffolk; Coleridge Community College and Parkside Community College in Cambridge; and the Open Academy in Norwich.
Simon Barnes, director of TLC, said his company offers a "totally unique" service at "very competitive rates". "Teachers are incredibly busy and have a very difficult job, and the heads we work with would prefer not to ask their staff to stay after school until 7pm or to come in on weekends to give extra tuition," Mr Barnes said.
"We are very cost-effective. And I think if a school is asking for help from us, then that is a sign of strength."
Heads' union the Association of School and College Leaders said it could be a good use of public resources. But the move was branded "appalling" by classroom union the ATL, which described it as a "market stall" approach to education.
Martin Freedman, head of pay, conditions and pensions at ATL, said: "I think it's just an appalling use of public money where a company can just set up shop in a school and flog off education.
"I can understand if a family decides to pay for extra tuition for their child if they can afford it, whether you agree with that or not, but for a school to make that decision to avoid employing extra teachers - I've never seen anything like this before."