In what is believed to be the first case of its kind, Russell Gray, who runs a property restoration company in London, will try to take out an injunction against the £21,900-a-year Marlborough College, where Princess Eugenie is a pupil, to stop it expelling his son Rhys, 15.
The 162-year-old Wiltshire school told Mr Gray that Rhys, who sat his GCSEs this summer, could not return because he had not worked hard enough and had an "exceptionally poor" disciplinary record.
The case will challenge the freedom of independent schools to expel pupils.
Mr Gray hopes the case will highlight the problems faced by parents of pupils who attend private schools, who he says have fewer rights than parents with children at state schools.
He believes that pressure to succeed in league tables is pushing private schools to rid themselves of average students to replace them with higher achievers.
In a witness statement which will form a key part of the case, which is being heard at Swindon County Court, Mr Gray said: "I am very concerned that the college is seeking to increase its standing in league tables by removing the less academically talented children. While Rhys will never be top of his class, I do feel that his academic performance is well within an acceptable range, and that Rhys is being sacrificed in order to improve the college's statistics.
"I also feel the college's actions are remarkably unfair. The college say they have almost complete power to remove pupils at their say so, in what is an incredibly broad and open-ended discretion.
"I had certainly not realised the relationship between the college and myself was so one-sided whilst I was paying over very substantial fees for years."
Mr Gray says Rhys should be allowed to return as long as he achieves good enough GCSE results to go into the sixth form and has not committed an offence which would warrant expulsion. While he admits his son is "no angel", the offences cited by the school are minor breaches such as chewing gum and forgetting his books, Mr Gray said.
Mr Gray said he had been "completely surprised" when he was told in May that Rhys would not be allowed to return to the school in September.
Although Mr Gray accepts that Rhys cannot remain at Marlborough if he does not achieve the required grades he says it is unacceptable to expel him before the results are published on 25 August.
Rhys, who believes he will achieve a mixture of A* to C grades in his GCSEs, said: "I think the school have behaved very unfairly. They didn't tell me that anything was wrong until a couple of weeks in to the summer term. I thought my behaviour and work were both fine. It hasn't been very good to have this hanging over me when I sat my exams."
The school stands by its decision to expel him. Nicholas Sampson, Marlborough's headteacher, wrote to Mr Gray in June, explaining that Rhys would have to leave because of problems with his academic work and discipline.
The school says it can terminate its contract with Mr Gray under a clause which covered pupils who were "unwilling or unable to profit from the educational opportunities offered".
Mr Gray's legal team will claim that this contract included the presumption that Rhys would continue into the sixth form and that the clause which allowed his removal should be legally void as it was unfair and vague.
Independent school associations believe it is the first time a parent has taken a school to court to try to prevent expulsion. But they say that independent schools should be allowed the freedom to ask pupils to leave.
Geoff Lucas, chairman of the Headmasters' and Headmistresses' Conference, which represents some of the country's most prestigious schools including Marlborough, said: "It does not seem unreasonable for a school to say that a child should go elsewhere."
A spokesman for the Independent Schools Council, which represents nearly 1,300 of the country's fee-paying schools agreed. "Independent schools by their very nature are able to decide who they educate."
A spokesman for the school declined to comment saying "it would not be in the best interests of the child".
Former pupils of Marlborough College
One of the principal founders of the British Arts and Crafts Movement. Also a writer, and an early founder of the socialist movement in Britain
Poet Laureate from 1972 until his death in 1984.
Art historian and spy working for the Soviet Union during the Cold War
Actor in many films, including North by Northwest (1959) and Stanley Kubrick's Lolita (1962)
NORRIS AND ROSS McWHIRTER
Twins who co-founded The Guinness Book of Records
Son of the singer Bryan Ferry and England's youngest master of foxhounds. Stormed House of Commons in 2004.
Served as Chancellor of the Exchequer, Home Secretary and Foreign Secretary
Girlfriend of Prince William.Reuse content