Some of the replies to the OP here use a typical Chinese trick: respond to a “straw man” issue that is not the complaint instead of addressing the complaint. It is true that anyone can pull this trick, not just TWese/CNese. It is also true this trick (among others) is encountered more often here or in CN.
The replies say it is common to have to do demos. Doing a demo is not the OP’s complaint and those here responding to the OP know this is not the complaint. Everybody agrees a demo is required to interview a teacher, a singer, a car mechanic, a doctor, a plumber, an engineer, etc. Harping the point is thumping the straw man.
The OP likely suggested using teachers to role play to accomodate the request for a 30 minute demo without teaching for free.
Asking someone to do a 30 minute demo is a [color=#FF0000]red flag [/color]that the boss is a fraudster. Accommodate the fraudster during the interview process and you won’t be surprised she is later trimming your hours when you’re not looking.
Yesterday, I was asked to do a 45 minute demo(why not a 1 year demo?).
Interviewing teachers is for the most part like auditioning actors. Is the person interesting to watch, organized, can manage the class, and does she know the material? One needs about 2-4 minutes to assess this. Nothing more is needed. Schools looking for 30 minute demos or 45 minute demos are tricksters and flagging them is a service to the community. Not flagging them, remaining mute when speaking up is needed, disserves us all … and bolsters the tricksters. Some folks might think 5 minutes is too short. Maybe they are right. But a half-hour? Or 45 minutes(Leader school in 內湖)?
This trick is like the interviewers looking for a writer … and … they request several stories/articles/essays/exam-question. The stated reason for the request is allow the TWese interviewer to check the candidate’s work(as if the interviewer would no good english from bad). Later, lo and behold, you find your sample in the next edition of their magazine/catalogue/book, etc.
As important as it is for the school to assess the teacher, it is important to know whether the interviewer is honest.