In order to accommodate teaching for the new sixth-form syllabuses, we want to operate "twilight" classes, outside the normal school day. We are not expecting our teachers to increase their contact time, merely to adopt a different pattern of working. Are the unions' objections to this reasonable?
While you are not adding to the teaching load, you are proposing to alter conditions of service.
The changes you propose may well have an impact on teachers'domestic arrangements, such as child-minding or evening commitments, and the quid pro quo that you are offering in time off at other times may not compensate for the difficulties caused by upsetting the established pattern.
There is nothing inherently wrong or unreasonable about your plans, but their successful implementation will depend on negotiating with the unions to find an acceptable solution. It may well be that a degree of flexibility will lead to an outcome which the union representatives will be prepared to recommend to their colleagues.