KBS made the decision on the 23rd, and explained, "Certain parts of Lee Hyori's music video for "Bad Girls" were problematic, so we decided it was unsuitable for broadcast." The problematic scenes were where the student uses a slingshot on the teacher, and when the teacher sexually assaults the students solving problems on the board.
KBS added, "Lee Hyori's label edited the problematic scenes and they have resubmitted the video for review. We're going to be reevaluating the video after watching the edited MV."
MBC has rated the MV for 15+ while SBS gave it a rating of 12+.
Source: TV Report