Kieron Williamson's extraordinary gift as a painter has been likened by our own art critic to that of the Old Masters. But he's still only nine. What does the future hold for such a prodigy?

Maroon tie flying from his pale blue school shirt, Kieron Williamson hurtles along the lane outside his new home wearing a pair of hand-me-down inline skates. It is not how you might expect to find an artistic prodigy on the cusp of an exhibition that will earn in excess of £100,000.

Two years ago, when I first met Kieron, he was a sweetly monosyllabic seven-year-old whose unusually proficient pastels and acrylics of the countryside around his Norfolk home had attracted praise and a waiting list of 680 buyers. Now there is a waiting list of 6,000, as Americans, Chinese and Germans clamour for a Kieron original. Paintings he sold for £2,000 have been resold for £10,000. His fifth exhibition opened yesterday at his local gallery in Holt and sold out in 10-and-a-half minutes, one painting fetching £15,595.

Two years is a long time for any child, let alone a prodigy. I wondered how nine-year-old Kieron would have changed, and how this unhealthy concoction of money and media hype might affect him.

"Oh, he's a little lord of the manor now," laughs his mother over the phone when I first call. Kieron, his sister Billie Jo, mum Michelle and dad Keith were squeezed into a two-bedroom flat next to a petrol station but, thanks to sales of his paintings, Kieron this year bought the family a detached house, an attractive former post office by a village church on the Norfolk Broads. Kieron wanted to move close to the home of his hero, the 20th-century landscape painter Edward Seago, so they did, and Kieron will take possession of the house when he is 18.

This is a major life change for the family, so it is a relief to find Kieron skating outside with Billie Jo and friends after school, like any country village kid. He is polite but also nicely self-contained; he has grown in confidence but is not unnervingly eloquent. His "yeps" of two years ago have been replaced by agreeable "uh-hums" and it is still a surprise when he suddenly offers three or four carefully considered sentences about his work.

The wellspring of prodigious gifts is endlessly fascinating. From Mozart to Picasso, we have debated whether genius is born or made, and how. Kieron's talent seems particularly miraculous. His parents worked as an electrician and a nutritionist, neither remotely artistic, and Kieron was an energetic five-year-old until they visited Cornwall on their first family holiday. As they admired the view of a bay, Kieron asked for pencils and produced a striking drawing. But perhaps Kieron's passion for landscapes had been quietly ignited by all the paintings collected by Keith and hung on their walls at home.

"You can't see gifted children in isolation. It's all within the context of the family," says educational psychologist Susan Lee-Kelland. "Picasso always used to say it's very important not to teach a child how to draw, which is interesting, because his father was a renowned artist, so Picasso learned at home, perhaps without realising it. The same is true of musical prodigies – they often come from parents who may be choir masters, or musical in some way."

Kieron used to paint on the kitchen table. Now, step inside his cosy, low-beamed home and the first room is his studio, cluttered with easels and paints precariously balanced on palettes.

"I like painting stormy skies and I've painted lots of the marshes, and I like painting the windmills," says Kieron. His work looks freer and more sophisticated than two years ago. He points to a painting of a huddle of marshland cattle under a glowering sky. "This is my favourite picture. I like the sky. That's the favourite sky I've done. I did a watercolour out on location and that night I wanted to do an oil. It's just down the road. The cows were tucked behind the tree so I decided to move them over there. I don't like moving things around because I don't like to do made-up things. I like painting what I see."

I assume the painting is a few months old. When did he finish it? "Yesterday," he nods.

As well as filling books with intricate sketches, he is painting in oils, pastels and watercolours. "I couldn't stop painting with pastels, but then I had started a picture and I didn't feel like doing it, and that tells me to do something different," he says. He paints most days. "I have to do something every day," he says, although life gets in the way. "I have this school project to learn about the planets and I have to do 68 star constellations, and that is taking up a lot of my time." He wishes he could wake up earlier than he does (6am) so he could paint more. "Painting is like my best friend," he says.

Kieron calls his media duties "fun" – he is being filmed by German, Danish and French TV crews this week – and if it wasn't, Michelle and Keith would stop it. In fact, they tried. Stressed and struggling to come to terms with the fact that Kieron had created a proper business – and needed his own specialist children's solicitor and accountant – Keith became ill. They asked Kieron if he would consider continuing painting but stop selling his work for a bit. "Kieron said, 'If dad is not well enough to support me, then can you support me mum?'" says Michelle. So she is now his full-time manager. They have resisted agents that could lock Kieron into contracts and are determined that he only paints when he wants to, and is not forced to paint on demand.

Do they worry about protecting Kieron's gifts while ensuring a "normal" childhood? "As parents, you're running through those ethical debates every day. Other people have the luxury of dipping into this with judgments and opinions," says Michelle wryly, "which they freely share." Keiron is in Year 5 at the village primary school, and he fancies being home-schooled so he could devote more time to painting, but Michelle disagrees: "I don't think that would be fair to him, because he has to relate to people and school offers a huge amount in terms of social networking and things like that."

If a talented child is determined to pursue their talent to the exclusion of all else, how much of their development should be decided by them? Should parents allow a gifted child to choose their own school? "The child's voice is really important. It's got to be part of the process but that's the key word – 'part'," says educational psychologist Dr Kairen Cullen. "The child is able to communicate what they need, but they've not had the life experience that others bring to the table."

Parents may be concerned that early promise does not fizzle away, but Lee-Kelland cautions against accelerating the intellectually gifted through their education, a popular view reinforced by the desperately sad experiences of various prepubescent Oxbridge geniuses from recent decades. Peter Congdon, an educational psychologist who has been assessing gifted children for more than 30 years, says research shows acceleration or "premature promotion" is overwhelmingly positive for children. Many young people with high IQs "relate better to adults and older children", he argues. However, Congdon agrees that "accelerating mental development is sometimes bought at the expense of social and emotional growth".

"Try to keep things as normal as possible," is Lee-Kelland's advice. "Not to keep the talents under wraps, but don't make it the be-all and end-all. It doesn't do the person any good at all to be deprived of their childhood." She cautions against gifted children becoming too specialised – a talented musician or footballer who suffers an accident may never be able to play again. "It's about creating a rounded person and giving them lots of opportunities. An artist is fostered by the whole of their lives and experiences. When you look at a great painting – or a piece of music – it contains emotions and feelings," she says.

Kieron, it is clear, has an acute sensitivity towards the countryside around him, and is profoundly aware of the shape and the order of things. His current enthusiasms are Romantic: wild landscapes and ruins. His parents took him to How Hill, a beautifully preserved historic house nearby, and Kieron "was mortified, it was so well maintained," says Michelle. He prefers St Benets Abbey, a desolate relic on the Norfolk Broads.

Kieron meticulously notes the changes in the sky, air and autumn colours when walking – and taking photographs – in their neighbourhood. "Everyone keeps saying there's no wildlife on the Broads but there's marsh harriers and kestrels and deer," says Keith.

"Chinese water deer," adds Kieron. He loves the changing of seasons. What's his favourite? "Winter," he says decisively. He can't wait to see the marshes flood and the snow fall.

At nine, this artistic intensity is still combined with complete normality. Kieron loves football and watches Formula 1 with his dad. What would Kieron like for Christmas? "The new Leeds away kit," he says. "I want '4' and 'Kieron' on the back as well." (His dad is a huge Leeds and Billy Bremner fan.)

"We don't want art to be his only passion," says Michelle, turning to Kieron. "I think you will have a varied life, because you'll want that."

"Uh-hum," nods Kieron.

Is he excited about his exhibition? "Yep," he says. "I don't mind what will happen as long as people like my work and they give some comments."

And with that, Kieron hits the button on the remote control and settles down to watch The Simpsons.

The expert view: Jonathan Jones

Kieron Williamson is the kind of child prodigy who makes us marvel at the miracle that is human creativity. In the week that an exhibition of Leonardo da Vinci's works opened in Britain, here's a homegrown example of the kind of gift that made Leonardo's 16th-century biographer Vasari call him a "truly celestial". Williamson's paintings are triumphs of observation, skill and imagination. For a child of nine to paint such sensitive and accomplished landscapes is an awe-inspiring achievement. He displays not just a stunning mastery of drawing and painting but an emotional maturity, which is still more staggering.

Prodigies are rare in the arts because to write a poem or compose a symphony requires emotional maturity. Children who excel at the highest level are, for this reason, often musicians, because the technical mastery of an instrument does not in itself demand a diverse experience of life. Yet even Mozart, the most famous of all musical prodigies, evolved audibly from his youthful compositions to his truly great and profound adult works: his art gained power as it gained sadness, darkness, dread; all the adult things.

What makes Williamson so impressive is, therefore, the passion as well as technique of his art. He responds intensely to the landmarks and light of his native Norfolk, just as great East Anglian predecessors such as Gainsborough and Constable did. St Benets Sunset is a wonderful painting, with its brooding tower against a reddening sky. At nine, he's a Romantic. He seems fully aware of such comparisons, intimate with the masters of landscape painting: he has looked hard at Turner. To respond to such art at his age is in itself amazing – to emulate it, sublime. But he is not painting pastiches. His interpretations of the masters are creative, his vision genuine.

What happens to child prodigies when they grow up? In medieval Italy, according to Vasari in his 1550 book The Lives of the Artists, the famous painter Cimabue met a shepherd boy drawing with a stick in the dirt. He was so impressed with the boy's dirt drawings that he took him to Florence to train. The child was Giotto. He grew up to become one of the greatest painters of all time.

Giotto, and Leonardo for that matter, could rely on the unique training system for artists offered by an apprenticeship to a Florentine master. Let's hope our education system serves Williamson as well, for he is a very special talent.

• This article was amended on 14 November 2011. The original caption referred to Ludham, Suffolk. This has been corrected.