Hi Cameron
Has the superintendent formally advised you that this is a performance management process?
If he/the company were following their legal requirements on this, then they should be giving you some goals/targets you must achieve and be meeting with you regularly to discuss whether you have achieved them or improved in the specific areas they say need improvement. Is this happening? It would be called a 'Performance Improvement Plan' or something similar.
Also, have they been giving you records of discussion to sign during these meetings? As I would not be signing these discussions if you do not agree with the content of them.
If you strongly believe the allegations are not true then there is a chance this is leading into bulling & harassment territory. The Fair Work Commissioner deals with issues related to bullying and harassment in the workplace and management action that isn't carried out in a reasonable way may be considered bullying and harassment.
I would be keeping written records of each of these meetings and what is discussed, and perhaps request that a Performance Improvement Plan be developed that complies with the Fair Work Act as that's the only legal way they should be performance managing you.
Please keep us updated with how you go.
Anna