Does magic subschool matter for the Spell Specialization feat?

Question

The Spell Specialization feat says:

Select one spell of a school for which you have taken the Spell Focus feat. Treat your caster level as being two higher for all level-variable effects of the spell.

Every time you gain an even level in the spellcasting class you chose your spell from, you can choose a new spell to replace the spell selected with this feat, and that spell becomes your specialized spell.

Does the feat only matter for the school or does the subschool matter as well?

Example: I have Spell Focus Evocation. If I use Spell Specialization on Magic Missile, school Evocation [force], can I switch it to Fireball, school Evocation [fire]?

Answer 1

Only a spell's school matters to Spell Specialization

The feat Spell Specialization says, in part, "Select one spell of a school for which you have taken the Spell Focus feat." The feat just doesn't care at all about a spell's subschool or its descriptors. A caster that possesses Spell Focus (evocation) can pick for the feat Spell Specialization the spell magic missile as easily as the spell fireball… or the spell wall of force or even the spell contingency.

By the way, the school of evocation doesn't have subschools like, for instance, the school of illusion has the subschools figment, glamer, and others. When a spell has a term in parentheses after the spell's school, that's a spell's subschool. When a spell has a term in brackets after the spell's school, that's a spell's descriptor. For example, the spell magic missile is in the school of evocation and possesses the descriptor force, the spell fireball is in the school evocation and possesses the descriptor fire, and the spell charm person is in the enchantment school, the charm subschool, and possesses the descriptor mind-affecting. This may all seem very pedantic—and, to a degree, it is—, but the game cares about these distinctions, like in the description of the feat Spell Specialization.

Answer 2

The text of the feat only mentions the complete school, so as long as it's in the same school it means subschool shouldn't matter.