I also went to the one you mentioned in TST last year and I didn't find it helpful because they gave us so-called 'tips' but didn't really train the kid.
Anyways, I went to another in CWB (also branches in Jordan, Kwai Fong and tuen mun) and I'm really thankful for the teacher's help because they trained up my kid to bow when you see a teacher, etc. It's a bit like playgroup but the things they play are the things they'll most likely ask in the interview.