A very simple (or stupid...) question about school powers :
Are the 1st level school powers usable at will, or just once per day?
If it's at will, it's a huge power boost to wizards: for example, Conjuration school, acid dart. For the 5-6 first levels of play, you have an attack that almost always hits (ranged touch attack) and does roughly the same damage as magic missile, and you can only use a few 1st level spells a day...
So, anyone to sort this out for me? ;-)