Wags suggest the simple phonetic method, used to weed out Tims in the days when bhoys wanted to be apprentices. This would involve the interviewer guiding the parent to a chair.
If the parent asks "Wherr?", they are a Tim. If the reply is "Wheare?", the opposite is true.
This could, of course, prove to be an unferr - sorry unfayre - blunt instrument so East Dunbartonshire will have to be careful, if not cerrful or indeed cayreful.
Interrogators will also have to dispense with that old favourite "what school did you go to?" in favour of "what school would you like to go to?" But that's progress.