But nearly four decades later, after a career as one of the Beatles and as a performer and songwriter in his own right, the teenage rebel has returned to the Liverpool Institute eager to pass on his skills and knowledge of the music business. Next week he will preside over the official opening of the Liverpool Institute for the Performing Arts.
After learning in the 1980s that his old school had been closed and the premises were falling into ruin, McCartney spent more than Pounds 1 million of his own money on an ambitious scheme to reopen it.
The building in the centre of Liverpool now houses probably the best-equipped training centre of its kind, with four recording studios, a 500-seat theatre - once the school hall - a radio studio, video editing suite and 30 soundproof rehearsal rooms, all designed and equipped to professional industry standards.
The first 200 students, aged from 18, arrived this term from all over Britain and from as far afield as Japan and the United States. Their BA honours degree in performing arts, accredited by John Moores University, gives a grounding in all aspects of the entertainment industry. Students specialise in music, acting, dance, performance design or enterprise management, but will also follow a core programme covering all these areas. So a music student will learn not only how to play in a rock band but also how to deal with a complicated contract and a dancer will have a basic understanding of marketing. Visiting professionals, including McCartney himself and singer-songwriter Elvis Costello, will do around 40 per cent of the teaching.
Mark Featherstone-Whitty, chief executive of the institute, has been an accountant, an actor and an English teacher. "You can't teach talent," he says. "But you can give people access to equipment, knowledge and interpersonal skills that will make them far better prepared for the world they will face. We don't see ourselves as part of the educational establishment . . . our closest links are with the industry."
There are no specific entry requirements: applicants are asked to outline previous work in entertainment and their ambitions. One of this year's intake has managed rock bands, one was a roadie, and another played in brass bands.
The project, first suggested when Paul McCartney visited Liverpool after the Toxteth riots, has been made possible by cash from the European Union, the Liverpool City Challenge Fund and the National Lottery. Sponsorship has come from companies including the German electronics firm Grundig as well as directly from Mr McCartney. The cast list of patrons includes Joan Armatrading, Lenny Henry, Mark Knopfler, Toyah Wilcox and Victoria Wood. Dr Richard Hoggart, George Martin, Dr Jonathan Miller, Andre Previn and Sir David Puttnam are also backing the project.
Inside the institute, the successors to Paul McCartney and fellow rock'n'roll fan George Harrison are working on their latest assignments. One group is pounding out a 1960s soul classic, while another is in more laid-back mood with a recent chart hit.
They are enthusiastic about their prospects. "I wanted to learn about performing and about the structure of the industry," says 26-year-old guitarist Vergil Sharkya from Vienna. "It's not the Sixties any more when you just picked up a guitar and went off to be an overnight success."
Music teacher Mike Lennon (no relation) says: "We're very liberal in terms of teaching method and the students taking responsibility for what they want to do. Usually institutions are organised towards a classical tradition and a body of knowledge every student should learn. But we teach according to what the student needs."
Susanne Burns, head of professional development, rejects the idea that paying attention to the business side of being an entertainer could stifle creativity. "We're not trying to turn them into accountants," she says. "But if you can't manage your own assets you're not going to be as successful as you might be." The quote from songwriter Ira Gershwin in the prospectus - "So which comes first, the words or the music? The contract" - puts it in a nutshell.
But what would the younger McCartney and Harrison have made of the new training school for rock'n'rollers? Should the Beatles have gone back to college instead of learning their trade in the clubs of Hamburg? Perhaps they would have poured scorn on the idea. But, like many people in showbusiness who look back in anger on youthful naivety, they might have benefited from a little more knowledge of contracts, copyright and finance. "Look what happened to the Beatles in the 1960s," says Suzanne Burns. "They were totally exploited. "