Dear friend,
I handle consulting services to provide Performance Management System (PMS). The issue that you have described is not new. It happens everywhere. Perceptual differences between manager and his/her subordinates are common. Subordinates often nurse grouse against their manager for under-rating. That is why when I design PMS, I do not leave room for "non-acceptance".
Now at this stage, you have two options. First one is tell junior firmly that the rating of the manager is final one and no disputes will be entertained. However, this type of management style will only suppress the conflict and may not resolve it. Embers of discontent may extinguish temporarily but these could flare once again. The another option is to understand why junior is refusing to accept the rating given by the manager. Could you segregate on what points there is agreement and on what points there is disagreement? As far as disagreement is concerned, is there evidence with the either party? Let your General Manager (GM) call both the parties and sort out the issue.
Cleft stick: - The issue has caught you in a cleft stick. Whichever side your GM gives the verdict, the other party could feel that it has been let down. Possibly authoritarianism of GM may not bring it to the fore and your organisation may create a facade of the harmony. Nevertheless, it remains to be seen how long it lasts.
Learning from the Incident: - The incident teaches to all the HR professionals in general and you in particular importance of measurement in the Performance Appraisal (PA). Subjectivity foments vagueness as well therefore, you may find out whether the PA is based on any vague parameters. Secondly, our job is not to solve the PA tussle between manager and subordinates but take steps to prevent it. The incident could be trend setter and next years onwards there could be more number of objections. Therefore, to avoid recurrence of such incident, you may require institution of robust PMS that is designed by the external consultant. Feel free to call me for further discussion.
Thanks,
Dinesh Divekar