She didn't bother charming the cover, casualy walking to classes with 'Developmental Psychology' tucked under her arms.
She'd expected questions.
From students.
"Have I been lax in assigning homework?"
"...no? Class is as challenging as ever?"
"Then, how do you find yourself with enough time to study a thirteenth subject?"
"...oh."
She earns her first potion's detention of the year and uses it to outline her theory to Snape.
"Object constancy. More than the notice-me-not charm, I want people to actively forget the protectee's existence."
"How will you rememeber to remove it?"
"...crap."
"Detention."