Children removed from their family home and placed in foster care achieve significantly more academically at the age of 16 than those who stay with their parents under the watch of social workers, according to the first research on the subject.

The children in foster care obtained GCSEs on average six grades higher at than “children in need” — those who were regarded as at risk of being taken into care because of abuse or neglect, but were allowed to stay with their parents under scrutiny.

A six-grade improvement would have given children a much better chance of obtaining the crucial five C grades which open up a range of academic and vocational opportunities.

The longer a child was in foster care, the better the results at GCSE. The research by the University of Oxford and the University of Bristol, and funded by the Nuffield Foundation, used the results of thousands of children combined with interviews.

Foster care is often criticised for poor educational outcomes compared with the general population. Only 31 per cent of foster-children achieve five good GSCE passes or more compared with 69 per cent of all 16 year-olds. This is the first time that children in foster care have been compared with their closest peer group — children at risk of suffering neglect or abuse, although not serious enough to warrant removal from their home.

The study found the same improved GCSE results for children who were removed from parents to live with other relatives in formal “kinship care” arrangements. School absences, the timing and number of moves between foster placements and the type of school attended were found to have a significantly detrimental effect on exam performance.

Overall, young people in care who changed school in Years 10 or 11, their key GCSE years, scored more than five grades less than those who did not. Each additional change of foster-care placement after the age of 11 resulted in about one-third of a grade less at GCSE. For every 5 per cent of school sessions missed due to unauthorised absences, young people in care scored more than two grades less at GCSE. For every additional day missed due to exclusions, they scored one-sixth of a grade less.

Professor Judy Sebba, director of the Rees Centre for Research in Fostering and Education at Oxford, said: “In general, the longer the child was in foster care, the better they did educationally.”