The governors of a Jesuit-run school lost an appeal against a court ruling which gave a former City lawyer the right to pursue a £5 million damages action against them.
Patrick Raggett, 52, of west London, claims he was subjected to years of "insidious" sexual abuse by a teacher at Preston Catholic College, in Lancashire.
He alleges that, while he was naked, Father Michael Spencer - who died in 2000 aged 76 - measured him "to chart his growth", filmed him performing exercises, photographed him and touched him inappropriately.
Mr Raggett's case rests on the fact he did not connect the abusive experiences with years of under-achievement at work, a failed marriage and binge-drinking until he had therapy after an April 2005 breakdown.
But the governors of the college, which closed in 1978, deny liability and argued at a preliminary hearing at London's High Court last year that, even if the abuse occurred, the case could not proceed as it was brought outside the legal time limit.
However, Mrs Justice Swift ruled that the case could go ahead to a full trial.
She accepted Mr Raggett's evidence that Father Spencer had subjected him to episodes of sexual assault and that he was sometimes abused several times a week over a period of about four years until he was in his fifth year at the college.
Mr Raggett was seeking "very significant damages on the basis that the abuse had affected the whole of his career both at university and subsequently as a solicitor".
It will be for him, on the facts of the case, "to demonstrate in the light of the events that had occurred that the sexual abuse was responsible for the large claim".
Part of his claim is for past lost earnings of £1.78 million and future loss of earnings at £1.95 million.
