I’d been a teacher for about 20 years when I confided in a colleague that I no longer enjoyed teaching in inner-city schools. Not long after, the lead tutor on the Harry Potter films called me to ask if I wanted to teach some of the children acting in Harry Potter and the Order of the Phoenix. Since then, I’ve tutored young children working on the final Harry Potter films, on Assassin’s Creed, Jurassic World and The King’s Speech.

For Harry Potter, children would come into my classroom wearing their Hogwarts uniforms. Costumes can make lessons tricky because they’re often quite valuable and intricately designed. Even if a child just has one single piece of costume on, we’re not allowed to use things like ink, felt or glue in case it gets on the costume. Knowing this, I try to timetable any messier lessons for first thing in the day, before costume fittings.

There is no average day. I could be on call from as early as 8am, but I might not see my pupil until 3pm. Each lesson has to be a minimum of 30 minutes to count towards the weekly total, so if my pupil gets called away after just 20 minutes, we have to scrap the lesson from our records. Time is money on the filmset, so when you get a knock on the door saying they need your pupil on set, it’s not a case of finishing up what you’re working on – it’s put your pen down and go.

The maximum amount of time we can teach each pupil for is a maximum of five hours a day. It’s a rolling total, so you try to teach 15 hours by the end of the five day week, but you must have taught each pupil for 60 hours by the end of your four week block. It’s the difference between having a class of 30 children from 9am - 3pm and having a class of four children for a 12 hour day.

We can’t cover all of the subjects taught in schools because we don’t have the facilities, so we focus on maths, literacy and science. The work itself comes from the school, so I liaise closely with class teachers via email. My aim is that when a child returns to school, they won’t be sitting in the classroom thinking: “I have no idea what my teacher is talking about.”

The learning environment on set is less formal than in a school classroom. The children call me by my first name and when they’re tired, I’ve had them cuddle up to me reading books. But it’s important that they see me as a teacher figure, not a maternal one. I’ve learned that it’s not a good idea to be both a teacher and a chaperone. Sometimes the children are excitable when they arrive for lessons, so I have to remind them it’s not the time to sing or rehearse their part. They’re very adaptable though, and can usually switch hats quickly.

People think my job is wonderfully exciting and it is – every day is different and I get to glimpse behind the scenes as a film is being made. But it’s also hard work and can be a lonely life. As a teacher, your day is shorter than the rest of the crew’s who often work 15-hour days. You’re also working alone, whereas the other professionals onsite work in teams.

One of the highlights, though, is travelling. The furthest I’ve travelled for a teaching job was Kathmandu in Nepal for Doctor Strange. I’ve found myself in all sorts of bizarre locations. At the grander end of the scale, I’ve taught lessons at the Honourable Society of the Middle Temple, the Tate Modern and the Goring Hotel. But I’ve also taught in a tent on the top of a cliff in Cornwall, with winds blowing up a gale outside.

Normally though, you get a trailer to teach in and the children and I often decorate it like a classroom. I encourage the children to bring in things from home or pieces of work they’re proud of to put up on the walls.

The stress of the job is different from teaching in a school; time restraints and fitting all the legal hours into the schedule is the biggest challenge. My advice to teachers who are curious about tutoring on films is that you need formal teaching qualifications, a certain level of maturity and an awful lot of experience working in schools first because there are often no other teachers you can ask for advice. You’re a one-person department and you have to know what you’re doing.

It’s not a secure career; there are only so many films produced in a year that employ children on a full-time basis. Many tutors working on film sets do other tutoring on the side. There aren’t many of us, so we often pass work onto one another when an offer comes through that we can’t take ourselves.

But there was no better place for networking than on the Harry Potter films. For the big scenes set in the Great Hall or at Quidditch matches, there were about 400 children at any one time. But as the maximum class size on set is 12 pupils per tutor, I met many other teachers. Jobs for teaching on film sets aren’t really advertised, it’s all word of mouth. But once I was in the system, I started to get calls from assistant directors offering me further work.

When I started out as a teacher, I never thought I’d end up teaching on film sets. It really has been an unexpected twist.

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