Schools of magic (spell schools) are groups of related spells that work in similar ways. A wizard may choose to specialize in a school of magic, thereby gaining one additional spell slot per spell level while losing the ability to cast spells from an opposed school. This prohibition extends to spells cast from scrolls, but not to spells cast from other kinds of items. In addition, specialist wizards have a bonus (+2) to identifying spells (through spellcraft) from their area of expertise and a penalty (-5) to identifying spells from the opposing school. Alternatively, a wizard may choose to not specialize, thus keeping access to all spells.
The default schools of opposition, as set up by BioWare, are different from those in pencil-and-paper due to the limited selection of spells available in NWN for some schools. These defaults are as follows:
- Abjuration - opposed by conjuration
- Conjuration - opposed by transmutation
- Divination - opposed by illusion
- Enchantment - opposed by illusion
- Evocation - opposed by conjuration
- Illusion - opposed by enchantment
- Necromancy - opposed by divination
- Transmutation - opposed by conjuration
Note that the abjuration, evocation, and necromancy schools are not listed as opposition for any other schools. Therefore, spells in these three schools can be used by any wizard, regardless of specialization. In addition, cantrips can be used by any wizard, regardless of school and specialization.