According to The Gender Identity Development Service (GIDS), 969 children under the age of 18 have been referred to them due to gender identity issues, with almost 200 being 12 years old or younger.
Thanks to love and support from his family, friends and teachers, Ave has been able to become who he truly feels is himself. His mum, Fiona, tells us how she realised her child felt uncomfortable in the gender she was assigned to, and how she's determined to make sure her son feels happy throughout his journey as a transgender person.
My son hasn't been forced into being a boy - he's always wanted to be one, and we've decided to let him be his happiest. Parents like myself often feel like they have no choice but to hide away and keep their kids' identities secret - we're not doing that.
We'd had an inkling since Ava started nursery, when they produced a yellow gingham dress. Tears rolling down her cheeks, she declared: 'I'm not wearing that!'
The reaction didn't come as much of a surprise - Ava had never been one for girly clothes. For years, I'd insisted on buying elaborate Christmas Day dresses for her, but they'd be off within the hour.
'Don't worry, at least you got to take a nice picture of Ava with the dress on,' my husband would say, but I was confused - I didn't understand why she hated all the clothes I bought.
I tried buying boyish looking girls' clothes, but she soon realised I was conning her. She even started checking the inside the clothes to see what the label said.
'I'm not wearing that - it's for girls,' she would protest.
By 2014 I gave in and bought Ava boys' clothes from Zara. We took a trip to Paris, and one evening we went on a dinner boat cruise down the Seine.
Ava was wearing a little suit, a shirt and a tie with her long blonde hair loose down her back. While seating us, the waiter said, 'Would sir like to sit here?' and Ava was absolutely beaming from ear to ear.
'He thought I was a boy!' she grinned.
Once she'd got her own way with the clothes, Ava's determination grew, and she asked to cut her hair. I was absolutely gutted - it was so beautiful, with long blonde curls down to her bottom that had been growing since she was a baby.
Still, I said to the hairdresser that it was all coming off.
'I don't think I can do it,' he replied. 'Well, we're going to have to,' I told him.
After the first cut, Ava asked for her hair to be shorter and shorter - it stopped looking like a shorter trendy girls' hairstyle, and like an actual boys' cut. Within two months it was eventually shaved.
Ava now looked like a boy, and at eight and a half years old, I realised how much she truly wanted to be one.
'You need to know that this might be really difficult... some people might bully you, this is probably going to be the hardest thing you'll ever have to go through,' I told her fearfully.
'Yes, Mummy - I really want to be a boy,' she replied.
We made a deal. 'Over the summer holidays, you can transition to be a boy. If it works for you and you're happy, then you can go back to school in September as a boy,' I said.
That summer, we went to Turkey, and because nobody knew us, it gave us time to practice. We kept getting it wrong and forgetting she was now a he.
'Ava, Ava,' we'd call, and he'd say, 'You've got it wrong again - it's Ave, I'm a boy.'
It worked - he even won an award for 'most handsome boy' from the hotel staff. Stephen and I nearly died - we looked at each other with an expression that just read, 'No!' - but Ave was over the moon.
However, our joy quickly turned to nerves again when we had to go back through passport control.
'Well... you don't look much like your photo, do you?' said the security official to Ave.
'No, I don't - but that's because I used to be a girl. My mummy said it was okay, and I get to be a real boy now!' he replied, adding proudly: 'And I just won the 'Most Handsome Boy' award at the hotel!'
'You're very brave!' she told him.
'I know,' he said, and at the time he was - but later, he admitted to me: 'You've got to change my passport photo, I don't want to have to do that again.'
Ave has autism, specifically the type which was previously Asperger's. He's very bright, and spends hours on computer games, but hates school unless he really likes the subject.
Back in England, our GP referred us to a children's mental health and wellbeing service, who then referred him to The Tavistock Foundation. Our paediatrician explained that whilst most autistic children are boys, apparently a high percentage of autistic girls feel they can associate more with the male gender than with the female gender.
All the pieces of Ave's puzzle seemed to be falling into place. Before school started, I emailed Ave's headteacher to notify her of the change. The headteacher was great, seeking support from other heads who have experience with transgender children and also Mermaids, a charity for transgender children. The head had a letter drafted to inform parents of Ave's decision.
It was mostly well received, I know there have been some comments but we try to surround ourselves with positive people who support us. There was also a discussion as to which toilets Ave would use. Legally he can use either, but he eventually made the decision to use the disabled toilet (which he says smells better anyway!).
Despite the plans in place, the night before term began, I suddenly felt overwhelmingly panicked about Ave showing his new self so soon.
'You know this isn't going to be easy, right? People might bully you or say nasty things,' I warned him.
'I know, Mummy. It will all be fine, don't worry.'
Inspired by his confidence, I decided to write a Facebook post to all our friends and family explaining Ave's transition. It was met with so much love and support that I couldn't believe it.
'Well done you for posting this and for supporting Ave. He is very brave to make this decision but life is long and he can't go through life being someone he isn't. Good for him to do it and to all the family standing by him and supporting him,' commented one family friend.
Since Ave's transition, the headteacher has made changes to make school more gender-inclusive, like rearranging the registration lines in the morning. They used to line up by gender, but now line up in two groups in alphabetical order, and in P.E., the kids can choose whatever sports they want - netball isn't just for girls.
A tricky situation arose when a classmate decided she wanted to be Ave's girlfriend, but the headteacher called me to tell me how well he'd handled it.
'I'm really sorry but I can't be your boyfriend,' he had replied. 'At the moment it's just not right for me, and it's too complicated to explain to you.'
We've always known that Ave likes girls. He gets angry when other kids call him 'gay', because he doesn't feel he likes other boys in that way: 'Face up to it, Mummy - we both know that I'm not a real boy yet. I'm not gay, I'm just a boy,' he tells me.
I know that the sexuality part of Ave's transition may be complicated, but it's something we'll address when it starts to surface.
Ava with her sisters before her transition
He already has concerns about his body changing. He's self-conscious about his chest and hates wearing tight tops, and told the doctor he was worried because his nipples had become larger.
'I want to be a real boy,' he kept telling her, despite her reassurances, getting so frustrated that he eventually blurted out: 'I want a willy!'
He knows that he'll have to have operations to get what he wants, and that it will hurt. He said to me, 'If Caitlyn Jenner can be a girl, I can be a boy,' and he's absolutely correct.
At the moment, he tells everyone that his mummy said he can be whatever he wants to be, and that his mummy will sort it out - he's absolutely right.