Age specific questions from about 5 years to about 8 years. Younger: pre-schooler. Older: middle-childhood.
This age specific tag covers questions about kids after they start school, for the first few years, so say from about 5 years of age to about 8 years.
Not much of a rule of thumb for this one: when they start school then you're ready to move up to primary-schooler, until they have been at it for a while.