I currently go to Ai's classes
They're quite good - he works he pays special attention to stuff likely to pop in the HSC, which is something quite a few centers overlook in favor of just covering all the content
As opposed to Terry Lee, Dr Ai only makes you pay for lessons you attend (if you skip one, he's not stingy about making you pay bulk in the beginning for all lessons). He's also up for explaining stuff after class if you don't get it
Currently, phys and chem is on Fridays, from 4:30 - 7. (1.5 hours per each subj, $35 ea.)
Def. recommend him. As RivalryofTroll said, he does have an accent, but its slight and doesn't get in the way of his explanations.
btw, classes start again from 24/1/2016. pm me if you want his number to contact about joining
~Shumba