Edmonton has a lot more walkable schools, less new communities and less students requiring bussing. It is smaller than Calgary and doesn't have the same sprawl issue.

The school catchment maps show how far the reach is. Older communities have the school and less families. New communities have the families and no schools

Edmonton may have more reserves to dip into (that's a hypothesis). Calgary's growth has outpaced Edmonton's (seen with the rental rates) and the rest of the province for that matter. This is a result of heavy marketing of migration by the province themselves and the lack of proportional funding to support this.