A handful of classes, and dealing with whatever lunacy was currently occurring in the girl's lavatories on that particular floor.
Rather than taking the stair case back towards the dungeons, Severus Snape kept going, towards the source of the noise, knowing he would have been all too happy to bet several hundred galleons on the students involved.
Reaching his destination, Snape noted that the heavy door had somehow been wedged open. And sure enough, hovering at its entrance was Potter.
Inside the bathroom, Weasley was hammering relentlessly on one of the stall doors, whilst Moaning Myrtle flew in and out of the empty stalls, wailing and screeching about the boys being in the girl's lavatories.
He came to a halt behind Harry.
"Potter! Weasley! Is there a…" he began, dark eyes scanning the room. "…Problem?"
The boy in front of him went rigid, but didn't turn around.
"ANOTHER ONE!" Myrtle screamed, spotting him. "THIS IS THE GIRL'S LAVATORIES! HOW DARE YOU!"
"Silence you derisible banshee!" he ordered, before turning his attention back to the boys. "What is the meaning of this?"
"It's Hermione, sir. She won't come out," Ron told him, gesturing to the closed stall.
"I see. And you thought that by attempting to somehow break down that door, you would be able to remedy the situation?" Snape asked, drily.
Ron scratched his head nervously and shrugged.
"Well it's just… she won't come out, sir. And we've got Transfiguration now!"
"Go away Ronald! I'm not coming to Transfiguration!" Hermione called, from within the stall.