Are you paying the trainees as per the minimum wages act? They cannot compel you to pay overtime rate unless they put in work beyond 8 hours. In fact don't ask them to put in anything beyond 8 hours. The next batch can work in the next shift. If they threaten to shut the line, this is serious, you need to seriously think of discontinuing such people who have the attitude to hold you at ransom. They may create problems in future. If they are doing support activity, you can engage contractual workmen. That can be another option.
26th May 2015 From India, Pune