The Department for Education and Skills received the report last Friday but will not publish it until "early February" to tie in with other public-sector pay bodies.
If the review body agrees with a joint submission from the DfES, employers and unions, then heads will have to conduct radical staffing reviews and introduce a new allowance system by December 31.
David Hart, general secretary of the National Association of Head Teachers, said members needed guidance quickly. "We can't afford any delay," he said.
Nigel Middleton, director of the Head Support pay and conditions consultancy, said: "The timescale is already unreasonable. Any delay now just makes heads' task even more impossible."
* Mr Hart has responded to Mary Bousted, general secretary of the Association of Teachers and Lecturers, who said heads should "stop whinging and start planning" in regard to the workforce agreement. He said the remarks were "crass" and demonstrated the ATL's ignorance about decisions heads would have to make.