Failure to teach children vital life skills such as communication and self control is widening the gap between rich and p oor, according to a think-tank.
Children's future earning power is increasingly likely to be determined by whether or not they possess these soft skills, rather than just their exam results.
A report from the Institute for Public Police Research (IPPR) said the school day should be longer so pupils can develop these skills through after-school arts and sports clubs.
Parents should face fines if they failed to make sure their children attend the clubs and take part in drama, sport, music or martial arts, the think-tank suggested.
IPPR director Nick Pearce went on: "There have always been class divides in education.
"But in the post-war period there were no social class gaps in how children were socialised into developing personal and social skills.
"Now there is a personal skills class divide, and it is contributing in the decrease in social mobility.
"Adolescence is also being stretched at both ends, with children becoming 'teenagers' earlier and 'adults' later.
"For too many young people this transition to adulthood is complex, messy and unsuccessful."
The think-tank analysed surveys with people born in 1958 and 1970.
The report found personal and social skills - like communication, self esteem, planning and self control - became 33 times more important in determining earnings between the two generations.
The think-tank recommended that children learn these social skills through extra-curricular activities such as the Scouts, Cadets, martial arts, drama clubs and sporting teams.
The report also called for a ban on advertising through TV, newspapers and mobile phones aimed at primary school children.
"This will be a first step, while further consultation should be encouraged to determine the appropriate age limit," IPPR said.
A Department for Education and Skills spokesman said: "The IPPR's report raises important sets of issues to reflect on as we develop our future youth strategy.
"It is important not to lose perspective and think all teenagers are in crisis - they are not.
"The vast majority of teenagers are achieving more and enjoying more prosperous lives than ever before, as the report acknowledges."