The TES wiki says this about the 'Summon Durnehviir' shout:
The shout Summon Durnehviir functions as a conjuration spell unlike Call of Valor. Therefore, if there is already a creature summoned, the shout will replace the summoned creature, also, summoning something else while Durnheviir is still active will prematurely end him.
Also, summoning Durnehviir requires you to shout at (target) the ground unlike the other summoning dragon shouts, and like the Conjuration summoning spells.
Based on this, I'm wondering if summoning Durnehviir will also level up Conjuration like I used a Conjuration spell (assuming there are enemies around and I am in combat). Can anyone confirm or deny?