By the age of seven, children are already facing limits on their future aspirations in work, according to a report from the OECD international economics think tank.
Andreas Schleicher, the OECD's director of education and skills, says "talent is being wasted" because of ingrained stereotyping about social background, gender and race.
He is backing a project from the Education and Employers careers charity to give children a wider understanding of the range of jobs available.
Social mobility barriers
Mr Schleicher says children have begun making assumptions about what type of people will enter different types of work while they are still in primary school.
There are only "minimal changes" in attitudes towards career options between the ages of seven and 17, says the report produced jointly by the OECD and Education and Employers.
The report, warning of the barriers to social mobility, says too often young people consider only the jobs that are already familiar to them, from friends and family.
"You can't be what you can't see. We're not saying seven-year-olds have to choose their careers now but we must fight to keep their horizons open," says Mr Schleicher.
He is backing the Education and Employers' efforts to bring people from the world of work into schools, with the aim of widening access to the jobs market and raising aspirations.
"It's a question of social justice and common sense to tackle ingrained assumptions as early as possible or they will be very tough to unpick later on," says Mr Schleicher.
The OECD education chief will speak at an Education and Employers event in London on Tuesday, where the charity will announce plans to double to 100,000 the network of people who go into schools and talk about their jobs and career paths.
At present there are more than 50,000 volunteers, representing jobs from "app designers to zoologists".
The intention is to create "light-bulb moments" where young people can see a possible new direction and hear from role models.
Research for the careers report shows that young people often have very narrow ideas about potential job options.
The most common influences are the occupations of people in their family, the jobs they see in the media and the type of work they see as most likely for people of their gender and background.
'Out of reach'
The findings show that in primary school, boys from wealthier homes are more likely to expect to become lawyers or managers while girls from deprived backgrounds are expecting to go into hairdressing or shop work.
Boys from deprived backgrounds were particularly likely to want to go into careers such as sport or entertainment.
Mr Schleicher warns of a mismatch between the limited range of aspirations and the changing demands of the jobs market.
"Too often young people's ambitions are narrowed by an innate sense of what people from their background should aspire to and what's out of reach," says Nick Chambers, chief executive of Education and Employers.
"The importance of exposure to the world of work at primary age cannot be overstated," says Paul Whiteman, leader of the National Association of Head Teachers.
"The earlier children's aspirations are raised and broadened, the better."