Children are under increasing pressure to grow up and must be allowed a childhood, teachers have demanded.
Children were said to be less interested in playing
Members of the Association of Teachers and Lecturers said children's rights, such as the right to education, should include the right to a childhood.
Delegates at the ATL's conference in Gateshead said it was too "uncool" for children to be children.
Kay Johansson, a teacher from Denbighshire, north Wales, said "they seem afraid to play."
A teacher at Rhyl High School, she said: "In the schoolyard where I used to see children playing games that would keep them fit, teach them social skills and stimulate their creativity I now see groups of children standing around discussing who has the most expensive pair of trainers or the latest mobile phone."
Mrs Johansson has worked in the profession for nearly 40 years and said the children's values were frequently not their parents'.
"All too often the values and attitudes of our children are the latest offering of the young male advertising executive who wants to make a large bonus by increasing the profits of his latest client.
"With their own peer groups as role models rather than responsible adults they are more likely to find out about the very things we should be protecting them from.
"The more and more that children gain access to this adult world the more they believe they are adult.
"This idea is happily reinforced by the type of companies that produce sexy undies and seductive party clothes for six-year-olds and cheeky ring-tones for their phones."
She said none of this helped teachers do their jobs and children were being "robbed of their childhood".
Maxine Bradshaw, from Ysgol Llywelyn, also in Denbighshire, said there was no clear division between adulthood and childhood.
"Too often children are treated as equals rather than minors," she told delegates.
She told the conference about a poem written by a child in her class of eight and nine-year-olds.
"It read: 'Happiness is being able to pay the mortgage'.
"Where was that child's right to a childhood, free from the dangers of adulthood?"