Which school of magic do you prefer and why?

If Dimension Door and Flight are not available, then if I level up Air at all, it's last; otherwise Earth is a must-have — you'll definitely struggle without it on an XL map with underground, followed by Water, and well, if you can't survive without Berserk, then Fire as well. But if the map is looped around Dimension Door (the hat or book happened to be nearby), then obviously Air comes first.