Ah, well, yes. They're a bit more...a-advanced than most other types of spells. M-Metal tends to require enchantments and sigils and things of that nature. [ So yeah. Complicated Haruhi. ] W-Wood is of a living presence usually. So controlling it is much harder and easier for it to get out of the caster's control. [ He can't even begin to tell you how many times he got tangled up in weeds and trees and the like. ]

Hm. Air or water is usually the easiest to teach.