Every Defense Against the Dark Arts professor had a classroom deeply influenced by their personality or interests.
But ever since the Dark Lord cursed the position, not every professor had as much time to pack up when leaving as Patricia Linnaeus did. Take the professors after Harry enrolled: the first, Quirrell, turned to ash; the second, Lockhart, had his memory wiped by "Obliviate" and moved into a permanent ward at St Mungo's. The third, Remus, left in a hurry of his own accord. He had practically fled Hogwarts, taking only the luggage he carried with him.
Everyone had something they feared. Remus's parents had met because of a Boggart. At the time, a wild Boggart had been about to attack his Muggle mother. She did not know how to deal with Boggarts and was chased through the forest by the shapeshifter until his father rescued her and shut the Boggart inside a matchbox.
Besides fulfilling their teaching duties, teachers also had to pay attention to their students' safety in class. In Hagrid's Care of Magical Creatures class, Draco Malfoy had been attacked by a Hippogriff, and Hagrid performed terribly for the rest of that year. Necessary protective measures were therefore essential during lessons. That was a teacher's responsibility, as well as the prerequisite for "enjoying freedom."
At Hogwarts, teachers chose the textbooks; they did not teach according to the textbooks. The headmaster gave teachers ample freedom to teach as they saw fit. Thus, on the floor of that Defense Against the Dark Arts classroom, there was a hexagonal polarization protection spell made from Dehoff bimetallic alchemical wire. Once the Boggart emerged from the wardrobe, it was trapped within the hexagonal polarization. No matter what frightening shape it took, it could not step beyond its bounds. The children, meanwhile, could stand