Inspiration hit while theatre director Paula Garfield was reading bedtime stories with her two profoundly deaf daughters. As always, the family’s reading experience was a bilingual process, and a mixture of both written English and British Sign Language. But how much did Garfield’s daughters know about the history of BSL, and what role models (other than their award-winning deaf mother) might they have to look up to? Could there be a show to explore these ideas, she wondered. Perhaps a series of books she and her daughters loved – Terry Deary’s Horrible Histories – might hold the answer.

Five years on, and Garfield is deep into rehearsals for Horrible Histories: Dreadful Deaf, a co-production between Garfield’s deaf-led company Deafinitely Theatre and Birmingham Stage Company. It’s a family show for children and adults, both deaf and hearing, and will feature comedy cameos from a range of famous deaf figures including the painter Quintus Pedius and the so-called “father of the deaf”, Abbé Charles-Michel de l’Épée, who established the first deaf school in Paris in 1755.

Paula Garfield, centre, at a rehearsal for Horrible Histories: Dreadful Deaf. Photograph: Becky Bailey

These famous deaf individuals, says Garfield, are rarely mentioned in mainstream society and Dreadful Deaf is partly about celebrating their achievements. But it’s also about helping deaf children – 90% of whom are born to hearing parents – to embrace deaf culture and begin to explore their history. Garfield explains: “It’s so important to me that deaf children understand something about where they come from, about having their own identity and about not being frightened or embarrassed about being deaf or using British Sign Language.”

When Garfield was growing up, hearing doctors and teachers argued against the use of BSL in the belief that it might harm literacy levels. It’s an argument that Garfield, eyes flaming, passionately counteracts: “There’s no evidence whatsoever that shows that the acquisition of BSL interferes with the acquisition of spoken languages. In fact, the evidence shows that it helps.” Garfield’s family still feels the impact of this professional advice today: “My mother continually brings this up with me. She says; I wish I’d never listened to those people. I wish I’d learned to sign so that I could talk to you properly.”

Theatres must be brave, take the risk and invite deaf directors in Paula Garfield

With this in mind, Garfield has created Dreadful Deaf just as much for hearing parents as for their deaf children. It’s a chance for parents and children to experience a BSL-led show together, and for parents in particular (who Garfield explains are often “terrified” when they discover their child is deaf) to see deaf actors happily go about their business, utterly at home in the spotlight.

This idea of creating a shared family experience – and perhaps helping to change attitudes towards BSL in the process – also informs DH Ensemble’s new show, Mathilda and the Orange Balloon. Written by Jess Kaufman, it’s an adaptation of Randall de Sève’s picture book about a curious grey sheep who dreams of a less sheepy existence and, when an orange balloon floats on to the farm, finds herself longing for a better, brighter way of life.

A brighter way of life … Mathilda and the Orange Balloon. Photograph: David Monteith-Hodge/Photographise

For director Jennifer K Bates, who learned sign language when she became frustrated that she couldn’t communicate with a deaf friend, raising awareness about BSL isn’t necessarily an explicit concern. However, just like all DH Ensemble productions, Mathilda and the Orange Balloon implicitly champions BSL. A hearing actor (Adam Jay-Price) and deaf actor (Mia Ward) narrate the show together, and deaf actor Hermon Berhane plays Mathilda, a sheep who refuses to limit her potential. At the end of the production, the children are invited to explore the farm on stage and express their feelings using “just their bodies”. I watch them sign together, instinctively creating their own rudimentary visual language.

After the show, Berhane (visibly worn out by an exceptionally interactive production) explains the motivation behind the show: “Deaf children need to have people to look up to. They need to think that anything is possible.” Berhane is also a fashion influencer and theatre has become a crucial part of her identity: “Six years ago, I went travelling and I sort of discovered myself. I thought: there’s something missing inside. And it was acting.”

It’s a sentiment echoed by Garfield, who tells me that theatre “saved her life”. “I started performing theatre at 18. I became alive because I could start to sign. I felt like I had something of value to contribute. I could tell stories, share my experiences, and connect with a hearing audience.” But when I ask Berhane about the training she has received as an actor she replies in BSL, one hand chopping down hard on the other. It’s the sign for barriers: “I’ve never had college or drama training because of barriers. I struggled to find a way through.”

Horrible Histories in rehearsal. Photograph: Becky Bailey

There is just one drama course for the deaf in the UK – one that Bates helped initiate at the Royal Conservatoire of Scotland – and it is only open for admissions every three years. It isn’t enough. Garfield is agitating for change with Deafinitely Theatre Youth, the Hub (a training course for young deaf people who want to work behind the scenes), and has plans to create a Deafinitely Theatre drama school. But UK theatres also need to get involved, says Garfield: ‘They must be brave, take the risk and invite deaf directors into their theatres. The deaf community has a lot to offer the artistic community.’

When I speak to Berhane about the drama course at the Royal Conservatoire, she sounds frustrated by its isolated status but excited about the opportunities it might offer. Berhane speaks of the recent deaf graduates from the course, her eyes sparkling: “They’re out there flying. They’ve got their wings.” She makes the sign for flying and I watch her hands flutter up, up and away.

• Horrible Histories: Dreadful Deaf is at Bristol Old Vic, 29 May to 1 June. Then touring until 23 June. Mathilda and the Orange Balloon is at TouchBase Pears, Birmingham, on 25 May.