The £21,900-a-year Marlborough College expelled Rhys Gray, 16, after his GCSE exams this summer and refused to let him return for the sixth form, arguing that he had not worked hard or behaved well enough during his three years at the school.
His father, Russell Gray, 49, who runs a property restoration company in London, is suing the school for breach of contract and demanding that Rhys be allowed to return. Mr Gray told Swindon County Court he believed the school's desire to improve its league table standing had been "a factor" in its decision to expel Rhys.
Marlborough said that it was Rhys's exceptionally bad disciplinary record and lack of "academic engagement" which cost him his place. Rhys had committed 398 offences that had warranted him being given disciplinary "blue chits", more than seven times the average. Mr Gray argued that the school had consistently underestimated his son's abilities and believed that he would only achieve B or C grades in his GCSE exams. But after Rhys achieved good GCSE results - including A-grades in all the subjects he intended to take at A-level - the school had switched its focus away from academic results and now cited discipline breaches as the main reason for his expulsion.
Rhys was expelled in May under a clause in the school contract which allows the ejection of pupils who are "unwilling or unable to profit from the education opportunities offered".
The family's case is that if the school had wanted to expel Rhys for discipline breaches then they could have done so - under a different clause in the contract - but they then should have given him a proper disciplinary hearing.
The case continues.