Schools that fail to meet workload deadline won't face punishment.
Joseph Lee and Karen Thornton report
Hundreds of schools that are expected to break the law by failing to implement the workload agreement by September will escape official punishment.
Teachers' leaders reacted angrily to an admission from the agency due to oversee workforce remodelling from April that schools which break the deal will not face sanctions.
Ralph Tabberer, chief executive of the Teacher Training Agency, admitted that the deadline for all schools to guarantee teachers 10 per cent planning, preparation and assessment time will not be met.
"It's going to be challenging: there will be schools that don't get there," he said. "We can use sanctions, but the approach that is being taken isn't about what sanctions we can use. It's about putting extra support in school."
Heads complain that they do not have the money to introduce the changes, and some are refusing to make savings by letting classroom assistants take classes.
A poll by FDS International for The TES reveals that nearly three in 10 teachers in Wales do not believe the guarantee of preparation time will be met -although 49 per cent say it will.
In Wales and England, 62 per cent of staff said the agreement was a good deal, but nearly a third of headteachers said implementing it had made their working life much harder.
The National Association of Head Teachers (NAHT) is due to hold an extraordinary general meeting next month to decide whether to withdraw from the agreement, after pressure from members.
Heads fear that even if there are no official sanctions, unions will take them to tribunals to enforce their members' new legal rights.
Chris Keates, general secretary of the National Association of Schoolmasters Union of Women Teachers, said a monitoring group consisting of employers, unions and the Westminster Government had responsibility for policing the agreement.
Last month (TES Cymru, January 14), the London-based group warned it was monitoring the situation in Wales, following concerns that some primary heads were "being resistant".
Ms Keates said: "The TTA and schools would do well to remember that the deadline of September 1, 2005 is statutory.
"It is not optional or voluntary and schools have had two years to prepare for this change."
Anna Brychan, director of NAHT Cymru, said: "These are contractual changes and teachers and school leaders expect them to be honoured.
"What we don't want to see is our members, particularly heads, being expected to make this agreement work without the support of the other signatories, whether the employers or others.
"There are considerable difficulties in financing the agreement. The difference between what the Welsh Local Government Association estimated was needed and the Assembly government allocated is about pound;23 million."
Gethin Lewis, secretary of the National Union of Teachers Cymru, said: "Our concern is that these plans haven't been carefully planned and costed, and it will be left to heads with insufficient resources.
"We insist the entitlement to planning, preparation and assessment time is honoured by headteachers and any breach will be exposed, but we do understand the concerns.
"Before September 1, we would want all the partners and unions to have meaningful discussions with both governments and local education authorities to ensure that the necessary resources are provided."
An Assembly government spokesperson said: "The minister has made clear that contractual changes for teachers underpinning the workforce agreement have legal force. Schools and LEAs must make this a priority."
FDS International surveyed 200 Welsh and 500 English teachers by telephone