My own personal opinion but... the mother of twins upset me a little by so flipantly saying just keep the child down if it becomes apparent that they aren't keeping up with the rest of the class (being that they started at a younger age). Having being held back in grade 3 it was a very difficult time for me and not one i would ever want to put my own children through. I'm sure my parents and my teacher were doing this in my best interest but emotionally it was so tough, i hated it and i've had to deal with it every since. I believe i started way too young and i paid for that academically, socially and emotionally.

Amoungst other reasons my children will start late and i'm greatful to be able to have the choice.