'Help us with work places'
Schools need more help setting up safe and high-quality "on-the-job"
placements for teenagers who would benefit from a less academic curriculum.
Headteachers are warning they cannot find enough long-term places, and have called on the Assembly government to urgently review the situation.
The government's learning pathways policy for 14 to 19-year-olds envisages a wider choice of work-based and vocational study programmes for young people who might otherwise leave school with few or no qualifications.
But Chris Howard, head of Lewis Pengam secondary, Caerphilly, said schools faced problems getting placements properly checked out for quality and safety.
Careers Wales, which manages 35,000 one and two-week work-experience placements for Year 10 and 11 pupils every year, has told schools that it is not funded to provide a similar service for longer-term placements.
Mr Howard, speaking at last week's National Association of Head Teachers Cymru's conference, in the Vale of Glamorgan, said: "Careers Wales tells us it sees a huge explosion in demand for this training in the workplace. But it can't service that.
"If I put a youngster in a workplace, I need to know he or she is safe, secure, properly bound up with health and safety, going through worthwhile experiences, and having some validation, recording and marking of what's going on. Careers Wales offers packages doing that, but it can't do it unless we pay for it."
Heather Guy, deputy head of Whitchurch high school, Cardiff, raised concerns about finding enough placements and the staff time needed to manage them - in her school, the equivalent of a full-time member of staff plus a fifth of a senior manager.
She added: "For many in rural areas it's going to be almost impossible to implement."
Mark Freeman, chief executive of Careers Wales in Cardiff and the Vale, confirmed that Wales's careers companies were unable to monitor the quality of long-term placements and provide health and safety and child-protection checks, because the issues were more complex.
For example, young people on long-term placements would come into contact with more employees than usual.
But he said the problem was being discussed, and pointed to north-west Wales, where a group of LEAs have contracted services from the local careers company.
He added: "It's a lot of work for employers too. They are providing supervision and support while the young people are at work."
Emma Watkins, head of policy at employers' organisation CBI Wales, said:
"Employers recognise the value of work placements because they realise young people are their employees of the future.
"But the additional burdens of work placements can put them off - particularly small businesses."
The government will publish a ministerial report on 14-19 next month.