There are still some areas that have not totally rolled out the full day kindergarten so that may be part of the age 6. Also from a needs standpoint kids that are 4-5 are still more likely to need our help to do things than a child over age 6. Age 6 has always been that magic number as in that is what is used in the rules in effect now meaning those in grade 1 and up.

Also not everyone sends their child to JK/SK because it is not compulsory to have some form of schooling in effect until a child is 6 years old so the rule will be based on the education act too.