Room 8 is Mrs Porteous' office as she is a Head of Year (Year 7).
It is hidden away in a corner of the balcony and has a door to Room 7. In Room 7 however, this door is so covered in memes and various printed off science jokes (mostly those that insult biology) that you cannot actually see it and to the untrained eye just looks like any bit of wall in Room 7.
One lesson whilst we were all working silently, and Miss Morris was teaching at the front of the classroom, we had put our heads down for one moment and when we looked back up Mrs Porteous was at the front of the classroom too, confusing and puzzling even the smartest in the class to the Head of Year's sudden appearance.
On the door you can actually see a sheet that says 'Fairy Godmother's Cupboard' which just further enforces that Mrs Porteous is actually capable of teleportation and uses the door as a cover story.