この教室のモットー The motto in this clsassroom

TANSTAAFL!(無料の昼食はない！) There Ain't No Such Thing As a Free Lunch!

"Oh,'tanstaafl.' Means 'There ain't no such thing as a free lunch.' And isn't," I added, pointing to a FREE LUNCH sign across room, "or these drinks would cost half as much. Was reminding her that anything free costs twice as much in long run or turn out worthless."

From "THE MOON IS A HARSH MISTRESS" written by Rovert A. Heinline by An Orb Book