Young female apprentices earn up to a fifth less than their male peers, according to a new report.
It suggests apprenticeships are also more likely to go to men due to discrimination in the labour market, and the types of jobs for which training schemes are available.
Unesco's 10th Education for All Global Monitoring Report suggests that when it comes to apprenticeships, a gender pay gap still exists in the UK.
It cites research which shows that female apprentices in the UK earn 21% less, on average, while doing their training.
And the wage benefit for a woman who has completed an apprenticeship is just 4%, compared with 20% for a man who has done the same training.
It says research shows that in general worldwide "apprentices are often more likely to be men because of discrimination in the labour market and the types of occupations for which apprenticeships are available".
"Young women who have taken apprenticeships get paid less in them, find it harder to get a job and receive lower pay once they are in work," it adds.
The current hourly minimum wage for a UK apprentice who is under 19 or in the first year of their training is £2.65.
The study also reveals that in the UK, schools play a less active role in helping youngsters to secure an apprenticeship.
Around two fifths (42%) of secondary school leavers who start apprenticeships apply directly to an employer, it says, while just 10% find them through their connections and 10% secure one through a careers adviser or teacher.
The report tracks worldwide progress towards six education goals set back in 2000.
The goals are to expand early childhood care and education, achieve universal primary education, promote learning and life skills for young people and adults, reduce adult literacy by 50%, achieve gender parity and equality and improve the quality of education.
The latest report finds that despite "significant progress" in some regions, few are on track to meet all six goals, and some are still far behind.
It warns that there is an urgent global need to invest in skills for young people.
The world's youth population is larger than ever, with one in eight young people unemployed and over a quarter stuck in jobs that keep them on or below the poverty line, it says.
The report adds that as countries continue to feel the effect of the economic crisis, a lack of youth skills becomes increasingly damaging.
Unesco director-general Irina Bokova said: "As a reaction to the economic downturn and growing youth unemployment, some governments are creating jobs, but neglecting to ensure that all young people learn the most basic skills they need to enter the world of work with confidence.
"Many, and young women in particular, need to be offered alternative pathways for an education. Unsurprisingly, we are now witnessing a young generation frustrated by the chronic mismatch between skills and work. These young people should not be seen as a threat. It is to everyone's benefit that we quickly start realising that they represent an opportunity."
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