Schoolchildren had been trickling into colleges for about a decade when the Government decided to make it a flood in 2002.
It was felt that giving younger teenagers more chances to study vocational subjects would help those who were put off by academic work or wanted to pursue more practical interests.
About 40,000 students started on the increased flexibility programme, rising to 120,000 last academic year. Most secondary schools and colleges have formed partnerships to place schoolchildren on vocational courses.
The National Foundation for Educational Research concluded in 2005 that the programme was particularly effective for those of lower ability. But lecturers complained that their colleges were becoming "like Grange Hill"
as unruly school children arrived.
Lifelong Learning UK, which oversees the training of FE lecturers, said dealing with under-16s was one of the main concerns of lecturers calling their helpline.
Ofsted inspectors said that the courses offered were failing teenagers, although the scheme improved over subsequent years.
Schools and colleges are supposed to jointly negotiate selection criteria, funding and behaviour policies, which should prevent colleges from suffering financially or becoming a dumping ground for troublesome school pupils.