Courses for hundreds of students have been axed as toughened guidelines curbing franchise deals - where colleges pay others to run programmes for them - begin to bite.
To comply with the law colleges have had to abandon those sixth-form programmes run in schools which they fund and oversee but which are taught by school staff.
The Further Education Funding Council said colleges could only operate the courses if they provided all or most of the teachers.
Programmes franchised by Eccles College to Irlam and Caddishead Community High School in Salford have fallen foul of the new rules. The college, which attracted 30 16-year-old students on to intermediate general national vocational qualification programmes this year, is to axe repeat courses planned for September.
The courses were taught by school staff but monitored and funded by the college, which enrolled the students.
Eccles has offered the 32 teenagers enrolled for the autumn places on the same courses on its own campus.
A proposal for a franchise deal between Carshalton College, Surrey and nearby Riddlesdown High School has collapsed since the FEFC announcement. Plans for a sixth form staffed mainly by the school were advanced, but partners had to "go back to the drawing board", said a college spokesman.
The school has now found an alternative, non-college partner to run its sixth form and the 86 pupils enrolled will be able to stay on in September. The college insists it is confident a solution could have been devised which complied with the new rules.
Two franchised sixth forms run in schools by North Derbyshire College have escaped the axe for a year despite the changes - but their fate remains uncertain.
In an ad-hoc arrangement exposing the confusion which persists over what is permissible in such partnerships, funding for the 200 sixth-formers currently half-way through courses will come next year from the local authority rather than the college. The switch is a temporary compromise because the programmes were almost entirely school-taught.
North Derbyshire principal David Bunch said college staff would continue to offer support at the schools while a long-term arrangement was devised. He said: "I can't say I am happy with the guidance, but we have had to be pragmatic."
One sixth-form collaboration which survived the tightening of franchising rules is a pioneering partnership between Manchester College of Arts and Technology and two local 11-16 schools which could prove a model for future collaborations.
The FEFC said the arrangement is not a franchise and is therefore legal.