The film Judy tracks the final year of Judy Garland’s life, the quintessential cautionary tale of child stardom. The list of tragic names since suggest things have not improved much – although some directors are trying

Judy Garland was a walking ghost story. Watch footage of the patron saint of child stars from any time after The Wizard of Oz, made when she was 16, and you see a woman haunted by the girl she never had a chance to be. How that haunting ended is the subject of a new movie, Judy, starring Renée Zellweger as Garland in 1969, middle-aged in London, broke and addicted. She was doomed long before then. The details – an adolescent starlet destroyed by studio executives – remain less ghost story than horror movie.

For generations, Garland has been a cautionary tale for kids who might venture on to the big screen. But the comfort of Judy, in theory at least, is that of a story safely in the past. How terrible the old times were; how long ago it was. Well, maybe. This summer, BBC aired the mini-series Dark Money, concerning a 13-year-old British actor abused by a Hollywood producer. The message came as a jolt, the suggestion of a film business that feeds on the young.

Did we need reminding? Brutalised child stars still appear in our films and TV shows. A few sustain robust careers: Natalie Portman is now open in her fury at the sexualisation she was put through as a teenager. Some fall but then return – how joyful to see the Netflix series Russian Doll after its star and co-creator Natasha Lyonne went missing for years. For others, the comeback is pending. In the next episode of the Terminator franchise, Lyonne’s 90s boyfriend Edward Furlong is due to reprise his role in the series that he first starred in at 14, decades of substance abuse and legal problems between (including charges of domestic violence).

Some no longer get involved. Given to wryly mocking rumoured reboots of Home Alone, Macaulay Culkin is now, in effect, in retirement in Paris, the consensus being that here is someone doing OK under the circumstances. Generally doing less well is Lindsay Lohan. And then there are the disappeared. Had they lived, Brittany Murphy would now be 41, Corey Haim, 47, and River Phoenix, 49.

Marbled through cinema history are the same awful stories, of girls bullied, as Garland was, into self-loathing; child actors of both sexes abused and commodified. As adults, they become punchlines. The executives are elsewhere by then. In the era of #MeToo, we have got used to the uneasy reappraisal of our favourite movies in light of their full backstories. A similar impulse kicks in with child stars. How comfortably can we watch the films of Tatum O’Neal or Drew Barrymore, working hard not to dwell on how many responsible adults saw them plunge into rehab?

But then, where would the movies be without ET or Clueless or The Wizard of Oz? We always need the kind of films that need child actors. Recently, there has been the glorious The Florida Project, the director Sean Baker’s bittersweet portrait of life in the budget motels next to Disney World, starring Brooklynn Prince, six when it was filmed. For the hard-to-shake Room – with a boy and his mother held captive by a sociopath – Lenny Abrahamson cast seven-year-old Jacob Tremblay. Both directors aimed to make their movies ethically, a film-making spin on the Hippocratic oath, “first, do no harm”.

Abrahamson emails from his Dublin office. There was, he writes, a commitment to “best practice. I wanted the experience to be a good and happy one for the young actor at the centre of the story.”

For Baker, speaking on the phone from Vancouver, old Hollywood loomed large. “I was incredibly aware of the unhappy history of child stars. So we went into the film very cautiously.”

Facebook Twitter Pinterest Edward Furlong, who will reprise his childhood role of John Connor, after years of substance abuse and legal problems. Photograph: Bobby Bank/Getty Images

Children in movies are so routine, you have to sometimes take a second to remember how flatly weird it is that, in this one corner of life, they exist in adult workplaces – which all film sets are. In any other context, it would be the stuff of comedy (or child labour outrages), building sites filled with schoolkids, pre-teens in meeting rooms on swivel chairs.

The formal response has been regulatory: limits on working hours, constraints on the kind of scenes they appear in. But regulation only goes so far. The British casting director Shaheen Baig has spent much of her career working with child actors, including on early roles for Jamie Bell and Tom Holland. “Productions are good at covering themselves legally,” she says, “but doing the right thing needs something else. Hiring people to work with kids who actually like kids should be a given, but it isn’t.”

One problem is that a first step on set tends not to lead to a creative magic kingdom, but fraught commercial reality. At auditions, a film-maker is desperate for the face who could make or break their project. Traditionally, there is little chance for reflection on how they might handle the next 20 years. Baig says that psychological assessments of child actors are sometimes carried out in British TV, but mostly to mitigate sensitive subject matter. Abrahamson spent considerable time with Tremblay before shooting Room, until he was satisfied that Tremblay would at least find this film healthy and rewarding. “The bigger question of whether a child will benefit long-term from being in films is largely unanswerable.”

Baker made efforts to de-stress the set of The Florida Project. “We would make a point of saying: ‘This is not what you have to do in life. This can just be one fun summer.’” Yet for many the stakes start high. Some kids may be having fun. Others are grim-facedly launching careers. The role of Disney World in The Florida Project was poignant, the corporation long acting as a juvenile production line from which Ryan Gosling (Mouseketeer 1993-1995) is just one graduate. Zendaya, star of the wildly successful Gen Z series Euphoria, got her break at 13 on the Disney Channel sitcom Shake It Up.

Economics matter. Gosling, raised in a single parent family, has talked of his headstart as a financial godsend. But the role of parents in the story of the child star can be complex, arranged on a spectrum with loving support at one end and pathology the other.

Dark Money hinted at an abyss beneath the film business. More common problems are in plain sight. Culkin used a rare interview on actor Marc Maron’s podcast, WTF, last year to defend his childhood friendship with Michael Jackson – he also offered to show Maron the scars left by his father, Kit. Parents require as much scrutiny in auditions as children. “If I feel the success of the child is more important to them than the continuation of a good childhood,” Abrahamson says, “I would not feel comfortable casting the kid.”

Whatever drives a child to start acting, it can leave them deeply vulnerable. Money explains a lot of adult cruelties – Garland was fed amphetamines by MGM to keep her clocking up 72-hour shifts – but even money is sometimes just a veil for other motives.

The film-maker relies on everyday solutions – to use talent agencies with spotless reputations; to talk and talk again to parents. Baig proposes a checklist touching in its simplicity – let children know if they haven’t got through an audition; ensure those who do understand it might never happen again; have someone checking teenage actors are eating properly. “And don’t disappear on them after the film comes out.”

Facebook Twitter Pinterest Brooklynn Prince in The Florida Project. Photograph: Allstar/Freestyle

Abrahamson is unsure if the movies have reformed. “Where there are power imbalances, the danger of abuse will always be there.” But, he says, #MeToo has made toxic behaviour of all kinds less acceptable. I ask if he would let his own children act in films. One already wants to, he replies. “Like any sane parent, that scares me. But I will support her.”

Prince and Tremblay have been busy since their breakthroughs. Prince, nine this year, is to star in Home Before Dark, the new Apple series about the real-life pre-teen news reporter Hilde Lysiak. Tremblay, 12, can be seen in the Seth Rogen-produced comedy Good Boys. Abrahamson admires Tremblay’s parents: “Down to earth, in no way pushy.” He also acknowledges the fame the actor already has may one day need unravelling. “There’s no before, no normal bit to compare to.”

Baker and the Princes have kept in touch. He is painstakingly respectful of their choices, fractionally anxious at the scale of their daughter’s career. “My concern for any child is that they are mixing with other kids, but I know the family are aware of the hazards around child stars, and battle those, and keep her socially connected.”

He says that, at the height of the 2018 awards season, with The Florida Project in contention for prizes, he saw Prince and Tremblay together at an industry party. They were passing among the adult guests, stopping to chat and sparkle. “Almost mingling.” They looked, he thought, like adults in miniature. “And it was cute and fun and they were playing it up. But it also made me hope that it was temporary, that it wouldn’t become a regular thing. Because it’s not a regular thing. And they aren’t really adults.”

Judy premieres on 31 August and opens in the US on 27 September, in the UK on 4 October and in Australia on 10 October