Parents should keep a check on post delivered to their children to help keep them safe from online predators, it has been suggested.
There are considerable risks to youngsters using the internet, and young people need to understand the dangers, according to Kamal Hanif, executive head of Waverley School in Birmingham.
Individuals attempting to groom youngsters online could send expensive gifts to encourage the child to keep in contact, he said.
Speaking at a session on keeping children safe from radicalisation and extremism at the Association of School and College Leaders (ASCL) annual conference, Mr Hanif also said that his school asks mothers and fathers to provide details of their holiday plans if they are taking children out of school in term time, and warns they may share the information if they think the youngster is at risk.
"There's considerable online harm, considerable risks there. It's making young people understand what those are," he said.
"It's very simply grooming, it doesn't matter whether it's radicalisation or sexual grooming, they use the same tactics. They'll ask young people to send through pictures, say 'you've got nice eyes, you've got nice hair'. They might try and prey on vulnerability as well, ask 'is mum or dad around?'"
If a child's father is not around, they may try to act as a father figure, Mr Hanif said, adding: "If they can't afford this they'll start sending through gifts or money or phones etc to keep that communication going and keeping it private."
He said he had told parents to be aware of what arrives through the door.
"I've come across a number of parents who said 'well actually, I just thought it was my child buying something off eBay',", the headteacher said.
"As one parent realised, 'there's really expensive stuff coming through and we can't afford that so how is my daughter managed to get it?' Looking into it further it was someone trying to groom her online."
"It's making parents aware, it's monitoring those sort of simple things that they can do at home as well as in school."
Mr Hanif also said that his school has "very robust procedures" in place for children travelling abroad.
"So if parents want to take a child away on holiday we've created forms where we ask where they're going to, who the contact details are of any relatives over here should there be an issue, contacts of where they're going to, where they'll be staying, is there are contact person there, and we will check all of that out.
"We also make it clear that should they be travelling to anywhere that there's government advice to say it's an area of risk, then parents will be invited in and that we will have discussions with external agencies. All of our parents are very aware that we have those procedures in place. So it's not just a case of 'I need some leave' or 'I'm taking a child away on holiday during term time'. The school will be following it up and may be talking to external agencies."
The Government has announced a series of reforms in recent months designed to tackle extremism and keep children safe.
Earlier this year, ministers said that schools are be told to set filters and monitor pupils' internet access, amid growing concerns that some youngsters are at risk of being targeted by extremist groups, and a number of high-profile cases involving schoolchildren travelling, or attempting to travel, to Syria.
Ministers said that, in some cases, young people had been able to access information about self-proclaimed Islamic State, otherwise known as Daesh, and foreign fighters through school computers.
A website has also been set up to give parents and teachers advice on protecting children from extremism.