A secondhand account of complaint, usually from a person of authority, or by someone who's the teacher's pet (if at school). A sentence of doom. Can happen if you've been sexually harrassing the teacher's daughter, sticking aluminum foil into electrical outlets, shoplifting, etc.
"Someone tells me you've been putting foil in the outlets at school. If you don't respect electicity, I can't let you have electronics in your room." "Someone tells me you've been mooning the principal. Don't you know you can get arrested for that?"