The call came as a Welsh Assembly committee was presented with damning new evidence as part of a major review into homelessness. John Puzey, director of Shelter Cymru, said much more needed to be done to help young people down and out at 16 and 17.
Giving evidence to the Assembly's social justice and regeneration committee last week, he said homeless under-18s were often treated like ping-pong balls by social services and housing associations.
His comments come as the charity is forced to bin one of its most successful projects with schools.
Co-ordinators of the learning peer project (see below) train young homeless people to deliver prevention lessons to Welsh teenagers in secondary schools. But funding from the National Lottery runs out at Christmas, leaving the scheme high and dry.
Jon Parvin, Shelter Cymru's peer learning co-ordinator, said: "Teenagers are much more likely to listen to other young people than a teacher. The feedback has been very positive and it is a real shame that the project is ending."
Schools are also hoping the programme will continue. Amanda Murphy, librarian at Swansea's Penyrheol comprehensive, said: "The peer learning project really changed the way pupils thought about homeless people.
"The perception was that homeless people are all tramps or drunks, but in reality some young people similar to them leave home after bad rows, never to return."
New research from Shelter Cymru reveals marital break-downs and domestic abuse are often major reasons for a young person leaving home.
In a report to Assembly members, Mr Puzey called for a national strategy embracing education, training and employment agencies to help young homeless people.
But charity leaders will also call for housing issues to be made a must-have part of the curriculum at their annual conference next Thursday at the Millennium Centre, Cardiff. It follows a major recommendation contained in a report on the effectiveness of a UK-wide teaching resource pack.
Evaluators found all Welsh secondary schools received the Housemate packs last year, compared with just 35 per cent in England, because Shelter Cymru had helped distribute them.
The packs, part-funded by the Assembly government, give teachers guidelines and ideas for 45-minute lessons on homelessness. However, it was recommended that the government should be lobbied to ensure the subject is compulsory for every school.
Mr Puzey said at the committee meeting: "Youth homelessness is certainly not going down and we are dealing with more cases every year.
"Current figures do not include what we call the hidden homeless."
Carl Chapple from the housing support agency Cymorth Cymru, told the committee that needy teenagers were being sent to adult hostels, leaving them exposed to bad influences from a criminal element, or being forced back to homes where they had allegedly suffered abuse.
Hard facts of homelessness
* The number of "accepted homeless" in Wales peaked in 2004 at 10,040.
* More than 35,000 children in Wales live in poor, cramped housing conditions.
* Most children living with homeless parents have changed schools several times and been unable to concentrate on work.
(from Shelter Cymru figures)