In the car park, children are twirling their wands and adjusting their robes. Others, meanwhile, are already in the Gryffindor common room. A few more are lurking outside Professor Dumbledore's office, or scanning the shelves in the potions classroom.
And, in another classroom, Year 4 students (aged 8-9) are already at their desks, waiting for their first lesson.
This is Hogwarts School of Witchcraft and Wizardry. Or, as it is more prosaically known, the Warner Brothers Studio Tour. Twenty miles outside London, sets from the eight Harry Potter films have been reassembled on two sound stages. Here, visitors can walk the flagstone floors of the Great Hall, admire the wizardly portraits in Dumbledore's office and search for supplies in Diagon Alley.
And, as at Hogwarts, there are lessons. And so Year 4 from St Thomas More Catholic Primary School in Hertfordshire sit at desks, ready for their induction into a magical world.
Will Daly, education and learning facilitator (as at Hogwarts, where the people delivering lessons are called "professor", no one here uses the word "teacher"), holds up a succession of costumes from the Harry Potter films for children to inspect: Sirius Black's threadbare and sagging overcoat; the rotting robes of the ghostly Dumbledore.
Then he brings out a battered, ripped and dirty corduroy jacket. This, he explains, is one of three versions of the same jacket, worn by actor Daniel Radcliffe as he - as Harry Potter - battled with death-eaters, Voldemort and the elements. There are collected "oohs" from the class.
Mr Daly grew up with Harry Potter. He read the books in all-night sittings, and queued up until midnight when a new one came out. "If I'd told myself two years ago the sorts of things I'd be doing now, I'd have gone absolutely mental," he says.
"When I first saw Sirius Black's jacket, I was like, 'Oh, my God. This is insane.' Now, I take it all in my stride. I'm in Dumbledore's office. Diagon Alley. I had to find a kid in the Ministry of Magic the other day. You don't think anything of it."
He is not the only post-pubescent Potter fan in the classroom. "I love the magical world of it," says Sally Meredith, the children's teacher. "I could really suspend disbelief."
But the point of the lesson is not simply proximity to Potter relics. Instead, it is to show children the range of specialised tasks that film-making requires. "Film-making is at the core of what we do," says Anne Lean, education and learning officer. "Harry Potter is a wonderful example, but it could be any film that we're talking about."
Before retraining as a teacher, Ms Lean was a vice-president at film distributor Miramax, working on The English Patient and Pulp Fiction. Now, she is eager to show children the range of careers available within the film industry.
"We need the next generation to be inspired to be film- makers," Ms Lean says. "I just think, one person, in one group, might be the next Steven Spielberg or Mike Newell. Or the next scaffolder.
"The thing that's important is that you don't need to be an academic: you can go into hair and make-up, construction, costumes."
"Harry Potter unlocks the door, brings them in," agrees Mr Daly. "We say to the kids, 'Has anyone noticed what's holding up the sets? Scaffolding. You can't make a film without scaffolding, any more than you can make a film without a director.'"
Ms Lean and Mr Daly deliver five lessons a day to primary and secondary groups. Teachers can select from 12 different lesson plans, covering skills such as pitching a film script and choosing camera angles. Each can be adapted to suit the students' age and curriculum needs.
And so today's class are learning to be costumiers. Each child is now given a pristine square of corduroy, and encouraged to decide what adventure its owner has been on and distress the fabric accordingly. Mr Daly hands out scissors, combs and fabric dyes: "Burnt umber is your dried blood, guys."
Ms Lean, meanwhile, bends over another table. "Wow. You're very destructive on this table," she says. "That's what I like to see."
Eight-year-old Finnuala Standen holds up her piece of fabric. "I think it looks like the person who's been wearing it has been in a lot of danger," she says. She pauses. "I might watch out next time I see a Harry Potter film, and see if I notice anything different."
Next term, the class will study stories set in imaginary worlds. "You can relate back to what we saw and what we did," Ms Meredith says. "It's a bit like going to a museum and seeing Roman artefacts."
"At this age, they need to have the wow factor, really, to get them writing. It's the awe and wonder that you want to bring into your lesson."
"Our school isn't like Hogwarts," nine-year-old Kieran Maher agrees. "You do normal things, like literacy and maths, not magic. It would be so cool to do magic and spells."
Next to him, Finnuala nods. "I could make my mum buy me an iPod."
The wizardry of film-making
Since Warner Brothers Studio Tour first opened the heavy Hogwarts doors in September 2012, more than 25,000 schoolchildren have had Harry Potter-inspired lessons.
The on-site classroom can hold up to 30 students and can accommodate five school groups every day. Each lesson lasts 45 minutes, and is usually followed by a few hours' exploration of the film sets and props on display during the studio tour.
The 12 available lessons can be adapted for primary, secondary and special needs students.