Above the big door leading to the viaduct. In order to get this one, you have to throw an item at it (for example, use the nearby stone vase) from the stairs in front of the gate.
Between two pillars in the corridor leading to Potions Classroom. Use Incendio on the web to get it.
In the room from which you can get to the corridor leading to the Potions Classroom. In order to get it, you must first break it and then repair it Reparo.
Opposite to the place where you found the crest there is a room and in front of the entrance - a corridor with a staircase leading down. Another crest awaits you at the end.
In the same room, go to the alcove with two armours and a stone bench. Turn around and look at the pillar on the left.
In the corridor on the 5th floor. Turn in the direction of the door leading into the room with a stone monument and look up.
On the top of the Clock tower, in the left corner.
On the top of the Clock tower, on a wooden beam behind the bells.
On the bottom of the Clock tower, on one side of the pendulum.
In the right corner (looking from the pendulum) on the Clock Tower Courtyard. Use Reparo to repair it.
On the wall in the left branch of the corridor (looking from the pendulum), which is located in the Clock Tower Courtyard. You need to use the Incendio spell to get to the crest.
After entering the Clock Tower Courtyard turn right (looking from the pendulum) and go through the narrow passage.
On the wooden bridge in front of the Clock Tower Courtyard.
In Stone Circle, look above the entrance leading to the wooden bridge.
In Stone Circle, to the left of the entrance to the stone bridge. You have to use the Incendio spell to get it.
On the left side of the path from Stone Circle to the Owlery.
On the wall by the entrance to the tunnel beneath the Owlery. In order to knock the crest down, use the dungobomb lying by the entrance. Set it as close to the crest as possible and then throw it so that the bomb doesn't hit anything in the air.
On the right side of the path in the tunnel below the Owlery.
On the wall before the exit from the tunnel below the Owlery.
On the outer wall of the Owlery.