Once upon a time, most children took themselves to school. The past is another land and people live there differently. Venture now within a kilometre of a primary school and it is clear that most children are chauffeured to school. Here is one study on active travel on the topic.
Only about a third of children walk or cycle to school. It does not change much with age and saw small increases since 2007 to 2016 (see graph below). The ACT Government at one stage put a primary school within walking distance in every suburb. Now with the rise of mega-schools this is less common.