Arelith

My character is a level 26 Sorcerer (Path of True Flame) and has ESF Evocation. Stats on MS haven't changed from base.
Furthermore, casting Elemental Sword on this summon does result in the visual effect and changes on it's character sheet, however no damage/+AB is applied to attack rolls.

Spell Focus: Evocation
Affected Spell List:
Hellball and Greater Ruin: Epic Spell Focus: Removes the 30d6 of backlash damage.
Mordekainen's Sword:
Spell Foci feats will provide a stat bonus to every summon that corresponds to the magic school associated with the Foci. Details can be found Here

Spell foci feats will provide a stat bonus to every summon that corresponds to the magic school. Conjuration affects Conjuration summons, Necromancy affects Necromancy summons.

Each level of focus provides:

+1 to all skills the summon has ranks in
+1 hit die worth of hit points (meaning, as if the creature was 1 level above in terms of HP, both adding base class HP and CON modifier).
+1 AB
+1 Damage
+1 AC
+1 Universal Saves