The power to close school sixth-forms will be returned to local education authorities when the post-16 education funding agency ELWa is abolished next April.
Opposition Assembly members this week threatened to derail plans for ELWa's merger with the Assembly government if its closure powers went to ministers.
But in a political trade-off, education and lifelong learning minister Jane Davidson gave a written pledge that she would delegate the powers over Wales's 171 sixth-forms to local councils - in exchange for opposition support for transferring the functions of ELWa and ACCAC, the Welsh qualifications, curriculum and assessment authority, to the government.
Welsh sixth-forms face an uncertain future as pupil numbers fall, and plans for greater collaboration between them and further education colleges are mapped out. Supporters say they are bastions of educational excellence and should remain. Unions have also criticised any moves to axe sixth-forms as mere "cost cutting".
But inspection agency Estyn has already recommended that small sixth-forms should close or merge into "super" sixth-forms catering for both the academic and vocational needs of pupils.
Estyn's recommendations have been welcomed by fforwm, the association of colleges in Wales, which says learners should be offered a more extensive choice of subjects than are available in sixth-forms. But schools are reluctant to share timetables and lose some of their brightest pupils to FE colleges.
Owen John Thomas, Plaid Cymru AM for south Wales central, claimed the minister had done a U-turn. He said sixth-forms, however small, should be kept at all costs.
Peter Black, the Liberal Democrat education spokesman, said: "I am delighted the minister has seen sense and caved in. She plays an important role in any appeals process and it would have been wrong for her to take over these powers -making her the proposer of closures as well as executioner."
John Graystone, chief executive of fforwm, said: "We recognise there is a real issue pertaining to the independence of the appeal process once ELWa is merged with the Assembly government. fforwm is keen to work closely to find the way forward."
Ms Davidson told AMs: "Young people need choices and the right kind of support. Schools and colleges must work together to deliver our agenda for 14 to 19 learning."