In a sunny classroom a group of children are constructing music festival stages out of cardboard; in the “playground” outside another class are learning how to throw a diabolo. It is Friday morning at school – but not as you know it.

This is Bearded Theory’s Festival School, where parents can enrol their children so they can spend a day in festival-themed lessons – without risking a fine for taking them out of school during term time.

Founded 10 years ago, the school at the Derbyshire festival – the only one of its kind in the country – has had children budget a festival in maths classes, write and perform songs in English and music lessons and take part in PE lessons run by Derby County and Mr Motivator.

The lessons, which take place for one day only on Friday at the festival, are different every year because about 90% of pupils are returning students. Places – which are free – are booked up in a matter of hours.

“We follow the national curriculum, and all the schemes of work, and lesson plans do, but we’re just a bit creative with it,” Dave Hancox, the school’s SEN co-ordinator, said.

As a director of children services specialising in learning disabilities, his role is to ensure all children can take part in lessons. In some cases, they have had 3:1 support from teaching assistants for children who require it.

“No matter what need that child has, we’ve never not accepted a child,” he added. “It’s probably the most inclusive school in the country, I’d argue.”

Hancox was recruited by Sally Booth, the founder and head of the festival school, when she found out he was the headteacher of a nearby specialist provision school. He is now one of the school’s senior leadership team.

“It originally came from when the laws changed around school absences,” Hancox said, with a lot of parents worrying they would be fined if they brought their children for longer than a weekend.

“So the discussion was had around all the team here, and we sort of said, well, why can’t we run a school here? And that’s where the original idea came from,” he said. “And 10 years on we’re still doing it.”

Parents register for the festival school earlier in the year, and staff will contact the children’s usual schools to have the day marked as an authorised absence for off-site learning – similar to a school trip.

It is open to children from reception to year 10, with 200 places available each year. “We don’t take year 11s because it’s GCSE time for them and they shouldn’t be here,” Booth said.

Often, Hancox said, the feedback from parents is that their “kids have engaged more at this school than they do at normal school”.

“We’re not constrained to classroom, we’re not constrained to four walls, we can adapt,” he said. “And ultimately, the staffing ratios here are probably better than most schools in the country. So the feedback is always really positive.”

“We all think that education doesn’t need to be in a classroom,” Booth, who previously worked as a teacher for 20 years, said. “It doesn’t need to be in a school with a trust, and an academy, and all of the paperwork and the KPIs [key performance indicator].”

“I’m not going to be measured on what they’ve learned today,” she added, “but the school will as a whole, because of the enrolments that come in next year, and the returners.

“I see the same names every year,” she said, “and it’s brilliant, but there’s still space for new people to come as well, so it works.”

Gemma Edwards, 38, an occupational therapist from Stafford, has enrolled her daughter Lillie, six, for a second year of festival school. She started in reception last year. “She loved it,” Edwards said. “She’s been talking about it all year, and it’s exciting to come back.”

Bearded Theory is Edwards’ favourite festival, she said, and “the festival school is part of that”.

“It’s amazing,” she added, “because you want to make the most out of the festival, it gives me and my husband some time. We have always loved festivals together, and now [Lillie’s] on board with it as well, but you do sometimes miss having that time together,” she said.

“So it’s nice for her to do something that she’s enjoying, but us to get a bit of a daytime together as well. So it’s lovely for all of us, really.”

Heather Bayley, 44, and husband, Jason, 53, have brought their daughters Lottie, 9, and Lola, 14, who is in year 10. “I think she’s a little bit sad it’s her final year,” Jason, an accountant said.

“We speak to a lot of friends, and people who go to other festivals – nowhere else does anything like this,” he added. “We’ve been to different sort of places, we’ve never come across anything like it. So it’s amazing.”

Heather, who works in a nursery, said: “The amount of prep that must go beyond the scenes, and with safeguarding, it’s deeper than just the kids coming to their classes and having a bit of fun,. I don’t know half the amount that Sally does, but I can only imagine from the work that I do.”

Victoria Mynett, 46, a paediatric nurse, has brought her eight-year-old daughter Sorori to festival school for the third time. She is such a fan of the festival school that she has volunteered to help there next year.

“I just know that this is going to nourish them, and this is good for everybody, and they cater for all the needs,” she said.“They’ve got the alternative provision, which is perfect for a lot of children, my eldest daughter did that last year. It’s brilliant.”

“Our school just embraced it and said, of course you can do that,” she added. “And then she brings back to school so much that she’s done, and she shares it with everyone, and everybody wants to come next year.”