4th and 5th Floor
The triad was the first to be informed by house elves. After that the Captains, and finally the house elves and patronuses were sent out so that security was awaken and all members were called on duty, regardless of their shifts.
They were split between two floors. The more experienced: Jamie, Alastor, Severus, Ginny, Ron, Emmeline, Marlene, Kingsley, Jazz, Tonks, Jacob, Gellert, Remus and Regulus were all on the fifth floor, while Dylan, James & Lily, Sirius, Alice, Frank, and Lucy, were all assigned to the fourth floor. The werewolves were split between the two groups as well and now, they would all have to stand their grounds and protect the castle from Riddle.
James was there ready to fight, but his biggest concern was getting Sirius out of this floor and away from the Dementors. Someone had to do it, but it couldn't be him, because all of his energy was thrown at the Patronus, casting one after the other stopping them from getting closer.