Proper attire during examination

How would you dress up when you sitting for an examination? For the past few invigilation sessions, I noticed that students did wear:

1. Bermuda shorts,
2. Slippers and
3. Baseball cap.

Jackets are common as the temperature at the examination hall may occasionally reaching 15C to 20C.

Should there be any basic rule and regulations on the attire while sitting for examination? Any comments?