The girls are acting weird

As you ride the bus in, you can hear the senior girls whispering quietly to each other.

"So they were really serious, right?"
"Did you do what you were told?"
"Is yours, you know, a... thing?"

The whole bus is buzzing with nervous energy by the time you make it to the school building.

You have no idea what's going on, but clearly the girls have been given a new rule to follow. And by the sounds of it, the rule isn't exactly the same for each girl, or something? Because they seem to be trying to subtly find out what rule, or rules, the other girls are following.

Your first class is English, with Mrs Fletcher. You take your seat in the back of the class, and the rest of the students slowly trickle in until the bell rings and Mrs. Fletcher steps up to the front of the room. A couple of the girls closest to you look quite uncomfortable sitting down, but you can't work out why.

"Good morning, class. Now your assignment last night was to read Jabberwocky for discussion in class, so who'd like to give us a quick synopsis?"

She pauses for a moment, waiting for volunteers. There aren't any. She points at one of the girls in the first row, a nerdy looking girl with curly brown hair named Sarah who she can usually count on for the right answer.

"Alright, Sarah, why don't you stand up and tell us what it was about."