One of the two major public buildings on Sydney's Bridge Street should be converted into a much-needed city school, says a group of prominent Australian architects.

The Department of Education building and the adjacent Department of Lands building are being offloaded by the Baird government for "no longer meeting their requirements" after more than a century of civic use.

"Public school in the making": the Department of Education building. Credit:Christopher Pearce

The architecturally prized landmarks, known as "the sandstones", are being sold on a 99-year lease through an international expressions of interest campaign closing on December 3. The marketing pitch describes it as a "rare" chance for a buyer to convert the two buildings into boutique luxury hotels.

But eight architects and academics are appealing to the Premier and Treasurer to keep the historically significant buildings in public ownership by realising the Education building's potential as "a Sydney city public school in the making".