Manchester College of Arts and Technology (MANCAT) is forming the partnerships with the city council's backing to tackle disastrously low staying-on rates.
The collaboration, described as a sponsorship arrangement, is understood to be the first of its kind in the country since colleges left LEA control. The closest comparison is Sheffield, where North Derbyshire College is franchising several school sixth forms, taking over responsibility for teaching and quality assurance.
In the Manchester scheme, MANCAT will work closely with the schools, lending its own expertise to develop vocational provision but also developing and using the skills of existing staff.
The college has so far used its own funds, but revenue will come via the Further Education Funding Council once the sixth forms start in September.
An FEFC spokeswoman said the scheme was closest to the arrangement between colleges and adult education providers where the provider did the teaching but the college provided guidance and support.
"This is very much tied in with MANCAT's work to increase participation in the inner city," she said. "It is not simply about getting more courses under its banner. "Effectively the college is opening a new centre in each school, " said principal Nye Rowlands. "The aim for us is not aggrandisement or profit. It is part of our service to Manchester."
The partnership, devised over three years of negotiations, exploits a loophole in a ban on sixth forms affecting all secondary schools in Manchester, all but three of which are for 11 to 16-year-olds. Though schools have been barred from changing their admissions policies to admit sixth-formers, the restrictions do not apply to colleges.
Manchester council has long been concerned at dwindling staying-on rates at colleges, with only about 30 per cent of 16-year-olds continuing education or training compared with 80 per cent nationally.
The low rate means MANCAT, with the three schools, will be seeking to draw in entirely new students who would otherwise have dropped out of the system. At present, 16 to 18-year-olds make up only 3 per cent of the college's 28, 000 roll.
MANCAT principal Nye Rowlands said a sixth-form might succeed where colleges failed. "If the school has good connections with the young people it can encourage them to stay on when they might not have adapted to the alien culture of a college."
Under the new scheme Newall Green High, on the Wythenshawe estate in the south of the city, Wright Robinson High in the east and North Manchester High School for Girls will each set up sixth forms using their existing buildings.
At Wright Robinson, headteacher Neville Beischer plans to admit 90 students in September, offering general national vocational qualifications and A-levels.
Mr Beischer said: "We've got a real problem with 16-19s. Most of them are out on the streets.
"This is one way of dealing with it. This school had a highly-successful sixth form. If this helps young people stay at school and get good qualifications, it has got to be a good thing."