C6's cousin used to have both their children in a similar school at West Pennant Hills.
The older one stayed there till he was in year 4 or 5 - left the school because he was being bullied on the school bus and the school and teachers will not do anything.
When they try to get him back into the normal school system, they discovered that he could not read!!! It was a hugh shock for everyone because he is such a bright child. Luckily, with intensive help, he caught up within a year.
My older 2 went to pre-school, the younger one went to childcare centre because I was working at the time and couldn't not fit in their 9am to 3pm hours.
my daughter goes to Montessori here in HK. She is 4y3m, and is currently learning 4-digit addition and 3-digit subraction. She is not ahead. It is really part of the Montessori curriculum. I strongly suggest you do a school tour and understand more about Montessori education before deciding. Theoretically, a well-taught child in the Montessori system can do multiplication and division as well as read simple books when they finish pre-school.