Fixing reality

"I suppose there's no way around this," muttered Jonnie. "I wish I knew why our wish didn't work."
The rock glowed. Jonnie's expression turned to alarm.
"Karyn... Mrs. Robinson made a wish on the rock while she had it."
"Yeah...?" Karyn began to look worried.
"She... she wished that this was an all-girls school."
"But hasn't it always been like this? Why would she wish for something that already exists?"
"That's just it... it wasn't always like this. When she made the wish, all of the boys at this school became girls... the only reason we don't remember it is that we didn't hear the wish."
"But... that means...," stuttered Karyn.
"Yes. Half of the girls we know used to be boys. For all we know, you or me could have been male until just a few minutes ago." She shuddered, picturing Karyn as a guy.
"Well, we can't just leave everyone like this! That would be like killing them, because their old identities would be lost forever. We should give them back their memories first, then sort out turning them back to normal."
"You're right," said Jonnie, "but we have to be careful. If I just give everyine back their old memories, they'll be sure to panic, and someone might get hurt. Plus, we should word it so that everyone remembers everyone else as they were, too, so as to avoid confusion."
Thinking for a moment, Jonnie grasped the rock and made her wish. "I wish that everyone remembered reality the way it was before Mrs. Robertson's wish, but that they wouldn't panic or become upset." The stone glowed, and...