Oliver, 15, had his phone confiscated by his parents a few months ago. This was after his mother discovered a series of graphic images of a naked 14-year-old girl on the device.
He had not been surfing porn websites. He had been given them willingly, so he claimed, by a girl at his school, who had taken the pictures of herself and sent them by text.
His mother said: "He just didn't recognise that there's a problem with doing this. Yes, they have had talks about it at school, but obviously nothing has sunk in."
If you are a parent of a young teen and feel confident that this is something your child would never be involved in, think again.
A report last month discovered that the great majority of pupils aged 13 to 14 are familiar with "sexting". The term conjures up images of Tiger Woods wooing barmaids with crude text messages. But it means something different to most teens. Sexting involves taking intimate pictures of yourself on a camera phone (even the cheapest pounds 3 pay-as-you-go phone has a camera) and sending them to fellow teens - often not your girlfriend or boyfriend.
The report by Plymouth University, in conjunction with the UK Safer Internet Centre, highlighted how widespread the practice has become. Prof Andy Phippen, who undertook the research across nine different schools in the South West of England, said: "We can confidently say that the vast majority of schools in the country have sexting issues."
From smart private schools in Oxfordshire to struggling state schools in Merseyside, the phenomenon has taken hold, fuelled by cheap, modern technology.
And now experts believe a popular mobile phone app that allows photographs to "self-destruct" seconds after being viewed is likely to encourage the trend further. About 50 million photographs are taken each day with Snapchat, which was launched by Stanford students Evan Spiegel and Bobby Murphy in 2011. It enables users to set a timer on both picture and video messages so that they will disappear between one and 10 seconds after being opened. Just before Christmas, Facebook launched its version of the app, Poke.
The NSPCC's Claire Lilley says: "Our research has shown that some girls are constantly pestered to get involved in sexting, which many of them find threatening and demeaning. Anything that increases this pressure is not welcome."
Prof Phippen makes clear that not all children are sexting; but all either know fellow pupils who've done it or have seen the images on other children's phones.
It is easy to dismiss this as a modern form of the passing around of copies of top-shelf magazines that went on in schools a generation ago - adolescents pushing boundaries and discovering the adult world for themselves.
But the experts warn that there are seriously disturbing aspects to sexting. The images children are taking of themselves are rarely simple nude shots. They are often crude imitations of the graphic images seen in hardcore pornography.
Jon Brown, head of strategy at the NSPCC, says the rise of sexting has been caused by a number of factors as well as cheap technology: "The access to hardcore porn on the internet is definitely influencing what is and isn't acceptable. It has upped the bar in terms of what people think is normal.
"Secondly, the diet of images and messages they get from music videos encourages people to think that certain things are normal. Combine that with the hormones that are coursing through the veins of a teenager, and it becomes a potent mix."
Indeed, speaking on BBC Radio 4's Today programme earlier this week, former High Court judge Baroness Butler-Sloss said she believes that the easy availability of sexualised images of young girls has a lot to answer for. It encourages people not to take the sexual abuse of children seriously. "Under the age of 16, it is a criminal offence to have sex with a girl - or a boy… [But there is now a complete] misunderstanding of, and overlooking of, the fact that the law is there to protect children. And you shouldn't start treating children under 16 as bad girls. You should start saying: 'How can these children be protected from this sort of behaviour?'?"
Anyone under the age of 18 is breaking the law by creating indecent images of a minor, even if it is of themselves. But the Association of Chief Police Officers says children will not be prosecuted for sexting. In some cases, though, when the police have got involved, the children have been reprimanded. This means that the incident is logged and would come up in a Criminal Records Bureau check years later. One distraught mother posted on the Netmums forum about her daughter, who had taken photos of herself: "She wanted to be a teacher, so not only has she lost all her friends, her boyfriend, her self-respect, but her future career is also in tatters."
Some sexting is reasonably good- natured, even if it can alarm adults. One 15-year-old girl interviewed by Channel 4 News said: "I think people sending pictures and receiving pictures of body parts is not natural, but is normal now - it's the new flirting."
Prof Phippen said he was encouraged by the emotional robustness of the girls he interviewed in the South West and how most were able to brush off requests for pictures from boys. In turn, most of the boys were "trying their luck", not being malevolent.
But this isn't always the case. Research at two London inner-city schools found that many of the boys' texts were menacing and predatory. Girls have ended up sending pictures to boys they barely know; the pictures then become a tool for bullying and the girls find themselves vilified at school.
Sexting can leave a "digital footprint" behind, too. Even if the messages are sent between two friends, who knows where they will end up? According to the Internet Watch Foundation, 88 per cent of sexting images end up on public websites.
Even apps such as Snapchat and Poke have loopholes that mean pictures taken on them don't truly disappear. For instance, a screen grab of an image can be taken before it self-destructs - and it is possible to download simple software that allows iPhone users to save videos on to their hard drives.
So is sexting now such a part of teen life that there is nothing to stop it? Brown says: "The genie is out of the bottle. We cannot get to a point where it just doesn't happen."
Will Gardner, chief executive of Childnet International, which encourages safety online for children, believes doing nothing is not an option. "Otherwise, where will we be in five years' time?"
Short of confiscating a phone, however, there is very little a parent can do. The messages are sent over a mobile phone network. No amount of firewalls or filters can stop text messages, nor can they scan the content of photographs.
One new mobile-phone service, Bemilo, allows parents to set the time of day their child can call and receive messages, and from which numbers. This, in theory, could halt cyber bullying - but it cannot stop children sending and receiving messages from friends.
Gardner thinks better sex education is crucial. He says it needs to take into account how social media has become part of a teenager's social - and love - life. "It is our job, all of us, to ensure that young people are making good choices when using the internet. To really think about the consequences - that is everything from personal data to cyber bullying and sexting."
Too many schools, says Brown, simply follow the rules when it comes to sex education in secondary schools. They just teach the biological facts, and have failed to keep track with technology. Teaching children when to say "no" online, or what is inappropriate to view, is just as important as knowledge of the reproductive system, he says.
But as one teacher put it: "Can you imagine if I taught a group of year nine [13- and 14-year-olds] about why pornography was degrading? I'd have parents marching into school the next day saying, 'How dare you teach my kid about porn?'?" The Department for Education says it is reviewing how it can update and improve its sex education guidelines.
All the experts agree that both parents and teachers need to talk more with children about sexting and why it is wrong, however awkward they find the topic.
Brown says: "It has to be co-operative. Any parent who says it is up to the school is shirking their responsibility. And any school who says it is entirely a family matter is shirking their responsibility."
One thing is certain: the ever more sophisticated technology is not going to go away. And none of the kit can teach the most basic lesson of all to a group of children. Think before you click.