The news comes as a consultant running courses for heads on implementing the agreement, claims that only a tiny minority of schools are aware of their full statutory obligations.
It follows last week's TES poll which found that 45 per cent of teachers had yet to benefit from the agreement.
Marking the first anniversary of the agreement's signing this week, the Department for Education and Skills claimed that 87 per cent of schools were taking "concerted action" on teacher workload.
But the figure, collected from local authority returns, may be an overestimate as it includes schools which "have plans in place" to implement the agreement alongside those which have actually begun to do so.
A DfES spokesman could not say how many were actually implementing the changes, but confirmed that the remaining 13 per cent had no plans to do so.
He said early findings of a Birmingham university evaluation of the progress made by the 32 pathfinder schools pioneering the changes showed evidence of a significant change in the time devoted to routine tasks.
But Nigel Middleton, a director of the Head Support consultancy which is offering heads courses on implementing the changes, said the vast majority he had spoken to were unaware of the regulations relating to the supervision required for support staff.