By Hannah Goff
BBC News, Manchester
Primary schoolchildren spoilt by their parents can cause disruption in the classroom by repeating manipulative behaviour used at home, a report says.
A minority of children were very manipulative, the report said
Research for the National Union of Teachers (NUT) suggested a minority of children threw tantrums, swore and were physically aggressive.
NUT boss Steve Sinnott is calling for more advice for parents who struggle to say "no" to their children.
The government says it recognises parents want more support.
Cambridge University held 60 interviews with staff and pupils in 10 schools.
The report was released at the union's annual conference in Manchester.
It cited examples of children who stayed up to the early hours and played on violent computer games.
It described a mother who celebrated the fact she had been able to get her five-year-old to bed at 1am instead of his previous bedtime of 3am.
It also told of a seven-year-old who smashed up his Playstation in a tantrum, then spent a week pestering his mother until she bought him a new one.
The researchers said some parents simply could not say "no" when their children demanded televisions and computers in their bedrooms.
Others would do "anything to shut up their children just to get some peace", it said.
Mr Sinnott said the problem lay with parents who were struggling with little or no help to bring up their children in a heavily commercialised world.
He wants advertising aimed at children to be banned.
"Parents are trying to cope by indulging, or by over-indulging, their youngsters," he said.
"A youngster who is being trained at home to get their own way by throwing a tantrum - I think it is pretty easy to see the impact that would have in the classroom."
He urged teachers and schools to give parents reasonable advice, but he warned they could not do it alone, and urged the government to tackle the commercialisation of culture head-on.
A spokesman for the Department for Children, Schools and Families said it recognised parents were under pressure to cope.
He said: "In the Children's Plan we learnt that parents want more support in managing the new pressures they face such as dealing with the internet and the modern commercial world, and letting their children play and learn whilst staying safe."
The spokesman said the government has also worked to give new powers to teachers to support them when it comes to disciplining students who act out.
The report's author Maurice Galeton said the problem was particularly acute where people lived in violent neighbourhoods.
He said: "Very young parents in violent and deprived neighbourhoods without the network of support that others get ... [have] a huge level of stress in their lives."
Margaret Morrissey of the National Confederation of Parent Teacher Associations said the problem of classroom misbehaviour was "not just about inadequate parents".
She told BBC Radio 4's Today programme: "We are putting into reception classes, in many cases, children who are four years and two weeks old. These are, in many parents' eyes, very little children - almost babies.
"If you are in a situation where you have got to work, you can't be with your child and you can't be giving it the sort of values that the older generation did."
The report also found the methods schools used to deal with poor behaviour were not working.
Some used a system of rewards and penalties to encourage children, but they often led to those who behaved the worst winning rewards for doing very little.