I'm not from here, but I live here. I can tell you:
the normal school-going age is between 6 and 7 years old. It would be unusual for a child to start school at 7 years of age.
I dont know if starting school at a younger age is allowed or not. Probably not - otherwise the ages of the kids would be very varied.
Of course, the norm is to go to kindergarten for years before that.