Okay so we know that there are 2 schools of magic (Arcanist notwithstanding). Thamaturgy and Conjuy. They also have access to 3 elements each. Thaumaturge get Fire, Ice and Lightning and Conjurers get Earth, Water and Wind. but Why?
Well think about it. Thamaturges claim destructive power. This is empaize by their control over deady elements (fire and lightning/levin burns and reduces to ash. ice freezes). Menawhile Conjureres are at one with hatire and the earth itself. And nature can be split into three parts: Land, Sea and Sky. Or in other words, earth, water and air.
As nature is associated with life. It also makes sense to let healers use those powers. Basically Conjury is nature, life and restoration, thaumaturgy is death and destruction. opposite sides of the same coin