I recently discovered the "Math Encounters Blog" and one of the blogs was a series of quotes he had used recently on his e-mails...
I found this one especially appropriate
From Admiral Rickover, 1983, commenting on how changing a failing school is one of the most difficult challenges around.... "Changing schools is like moving a graveyard".
I also decided I would steal this one for my regular personal use.... .."I don’t believe there is intelligent life on other planets. I believe they are just like us."
Perhaps adjusted for a classroom poster thusly: "I don’t believe there is intelligent life on other planets. I believe they are just like my students."