Borderline pupils are booked on to pound;300-plus private courses to boost league-table ratings.
Schools and local authorities are paying thousands of pounds to send selected pupils on GCSE and private A-level crammer courses over the Easter holidays.
Teenagers, typically on the CD borderline at GCSE, are offered tuition in classes as small as six as schools and councils try to improve their performance table rankings.
Justin Craig Education, the company behind the courses and the largest provider of Easter revision, is offering 10 schools a money back guarantee if the pupils fail to achieve their target grades.
The Hertfordshire company marketed its offer at a Specialist Schools and Academies Trust conference this week. Its leaflet read: "Improve your A*-C grade results by more than 5 per cent when increasing 10 students' exam results by just one grade."
At least five local authorities and 12 schools have paid for the courses in which private tutors spend several days working through exam questions with pupils.
They either stay overnight at one of five private schools or have a choice of five further venues: four state schools or a private day school. Justin Craig also runs courses "in-house" at state schools. Craig Halsall, Justin Craig's operations manager, said schools could typically pay pound;3,000 for three days' work with 10 selected students. GCSE prices for the public start at pound;315 for three days' tuition. Marilyn Craig, a director of the company, said some schools did not want to advertise their link with it for fear of upsetting the parents of children who were not selected to attend.
Tameside in Greater Manchester worked with Justin Craig in 2005 to provide revision courses for 100 CD borderline students, at a cost of pound;15,000. Since last year, it has used its own teachers and advisers to run a similar programme. Peter Jackson, a Tameside adviser, said Justin Craig had done a "great job".
The Warwick school in Redhill, Surrey, has lined up 13 CD borderline students to receive tuition in English from Justin Craig this year, at a price of Pounds 310 per pupil. Steve Rolt, the assistant head, said: "The pupils need good grades to get into college, so this support will be important to them." If the pupils get Cs, it will make an extra 3 to 5 per cent difference to the school's score.
Belfairs high at Southend-on-Sea in Essex used Justin Craig for revision.
Chris Childs, assistant head, said: "Students can sometimes respond to a different environment and a different tutor."
Margaret Wilson, head of King John school in Benfleet, Essex, said she would take up the company's offer for 20 pupils. "The students have everything to gain and I have nothing to lose," she said.
But Anne Guinamard, assistant head of Highdown school, Reading, said: "The idea of schools sending pupils to a crammer is about league table pressure.
It's not about education."
Margaret Morrissey, of the National Confederation of Parent Teacher Associations, said: "It is not fair to be taking money out of education for this, because it is giving help to a particular group of pupils. What about the others?"
Further reports, page 6 Leading article, page 26