Revised headteachers' contracts will require them to take account of the fact that teachers need time for a personal life.
Governors will have to make sure heads' workload does not upset their work-life balance. Heads of small primaries who teach classes will be given dedicated "leadership" time from September 2005.
But whether support staff will be available to ensure the changes take place is another question, as schools grappling with their budgets continue to warn of redundancies.
Eamonn O'Kane, general secretary of the National Association of School Masters Union of Women Teachers, said: "These developments will reverse the trend of oppressive workload that has been responsible for driving teachers out of the profession in recent years."
Future changes to teachers' contracts will set a 38-hour annual limit on covering for absent colleagues, and a minimum of 10 per cent a week non-contact time for planning, preparation and assessment.