Only three exist in England, but they were praised in the white paper. It said that they, like sixth-form colleges, provide both a "more adult environment" and "high rates of progression to university".
The first 16 to 19 school, William Morris academy in Hammersmith, London, was technically illegal for its first eight years until legislation changed in 2000.
The paper hints that such schools could also expand but adds that the Government sees them as "essentially taking the same role" as sixth-form colleges, even though they, unlike colleges, are overseen by local authorities.
William Morris principal Liz Walton said pupils enjoyed many of the freedoms of college students, but her institution was closer to a school in its size and pastoral support through tutor groups.