Real borstal inmates were used as extras, primarily in the riot scene. Director of Photography Walter Lassally stated: "The mix was so good that you couldn't-, unless you knew that this is an actor and this is an extra and this is a Borstal boy, you couldn't tell. The only time you could tell was at lunchtime, because they were absolutely ravenous. It looked like in the Borstal they were never properly fed because they were always looking. If you'd finished your dinner and you'd left something on your plate, they'd say, can I have that? They participated with great glee in the riot."
Producer and Director Tony Richardson continued to insist on selecting filming locations, which he'd begun with A Taste of Honey (1961), the first British movie shot entirely outside of a studio. According to Cinematographer Walter Lassally, location work was very difficult to sell to British movie financiers at the time. "They were afraid that a lack of sunlight would delay the shooting interminably. It was impossible to convince them that for greater realism, it was actually desirable to shoot exteriors without sun."
There is a running scene in which the camera catches both the rising sun and the setting moon. Director of Photography Walter Lassally recalled a critic writing of this scene: "'What consultation of ephemerides there must have been to capture that precious moment'...which only goes to show that critics don't know a great deal about how movies are made, because you can't possibly plan a thing like that. It would take forever, and fall well outside your schedule." The shot was actually one of those happy accidents that sometimes happen in filmmaking. Two cameras were set up, one with a wide angle lens and one with a long focus. It was pure luck that the two celestial bodies were caught.
Much of the filming took place in Surrey at Ruxley Towers, a Victorian mock castle built in the nineteenth century. From that, the filmmakers came up with the name Ruxton Towers for the borstal.
The romantic idyll on the beach at Skegness was filmed at Camber Sands, because it was closer to London.