The Knights of Christ I: The Journey Begins — Brendan Carroll

Christopher Stewart and Armand de Bleu are students in the most exclusive all-male school in the world. They are also serving as apprentices to two of the members of the Ruling Council of Twelve for the Order of the Red Cross of Gold. Christopher is completely devoted to his Master, Sir Ramsay, whereas Armand is much more loyal to the Order than his Master, Sir Argonne, who is cruel and heartless, but both apprentices are devoted to each other as friends and Brothers of the Order. Their world is turned up-side down when Christopher's Master is sent to the United States on an assassins mission that goes wildly astray. When Christopher learns that his Master's life is in danger, he enlists Armand to help him go AWOL to help Sir Ramsay.
While this is happening, some of the other students are getting into trouble with one of the less scrupulous, older apprentices who has an agenda not quite in line with the Order's traditions and expectations. Their boyish antics land them in a world of trouble, which could result in serious repercussions for all.
Armand and Christopher are soon found in violation of the Rules of Order, and both are punished, but sometimes punishment is a true learning experience. Niether of them will ever be the same.
(The Apprentice Diaries is a collaboration between Brendan Carroll, author of the Assassin Chronicles and D'Lani Elliott, teacher, mom and editor.)