g.t.b.y.h.s.t.
A loud and angry way to tell someone to go to sleep so they don't get in trouble at school
Your brother yelled: 'G. T. B. Y. H. S. T. or I'll tell your teacher you're a crybaby!'
You wrote on your wall: 'G. T. B. Y. H. S. T. or no pizza for a week.'
Your friend said in class: 'G. T. B. Y. H. S. T. or I'll make you eat your hat!'