The pair, who are in their mid-teens, came up with the idea after finding a key to the staff common room. They bought basic bugging equipment in a gadget shop, waited until the end of the school day, and planted the device in the staff room.
The girls, who attend a middle school in the capital, planned to listen in on a meeting the following day at which teachers would decide their grades. They were hoping to glean information that would enable them to get their grades improved.
The plan might have gone off without a hitch if one of the girls in her enthusiasm had not revealed all on Facebook, according to Metro. The girls were prosecuted for trespass and arbitrary conduct and fined 2,000 kronor ($270) each by Stockholm District Court.