Schools that fail to fully adopt a deal designed to ease teachers' workloads face losing control of their budgets and having their governing bodies replaced under plans being considered by ministers.
The TES understands that the Government is planning to introduce direct sanctions because there is currently no legislation in place to ensure the recognition of the school workforce agreement.
A TES poll last month found that 47 per cent of teachers said their school had not implemented the agreement in full.
The agreement, signed by Government, unions and employers in 2003, states that teachers should have 10 per cent of their time set aside for planning, preparation and assessment (PPA). They should not have to provide more than 38 hours' cover a year or carry out more than 20 clerical tasks.
But unions have become increasingly concerned that many schools are not abiding by the deal.
Discussions between unions, employers and the Government this summer established that, although local authorities can replace school governors or remove their powers over financial irregularities, they cannot do the same if the agreement is broken - even though it is legally binding.
An announcement of the penalties is expected later this autumn.
A Government source told The TES: "Ministers really want to nail down these workload reforms and are concerned that employers are not delivering them. We are working with the unions and looking at what we can do to toughen up existing legislation."
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: "Five years on, all schools should have implemented all aspects of the agreement."
The case of Nunthorpe School in Cleveland is believed to have played a big part in triggering the rethink. The NASUWT claimed its members at the school did not receive full PPA time and had to provide too much cover between January 2007 and July 2008.
The dispute could not be resolved locally, so officials from the Department for Children, Schools and Families and the Training and Development Agency for Schools were brought in.
Debbie Clinton, Nunthorpe's head, said she supported the agreement and had not broken it, but she was having "robust" discussions with a civil servant about certain unworkable aspects of the deal.
Sue Foreman, NASUWT executive member for Cleveland, said a speedier resolution would have been reached if the proposed legislation had been in place.
Mick Brookes, general secretary of the National Association of Head Teachers, said heads were "bending over backwards" to implement the agreement, but some teachers wanted to continue with duties that the deal outlawed.