The classroom Number system: Know it, love it.  It just makes it so easy when all of the kids have numbers - We're on a field trip and I panic for a second that we've lost someone - I can run through all of the numbers in order in no time flat and make sure we've got everyone.  We line up in number order.  I can easily call #1-5 to line up, #6-10, and so on.  The pockets where kids turn in their center work is numbered so it's very clear whose work goes where.  The cubbies are numbered.  The mailboxes are numbered.  And they can stay labeled exactly the same way for the following year!  
   Sometimes when we arrive at PE before the PE teacher's ready, we even do some math with the classroom numbers.  "6 x 3" I call out, and Zachary, number 18, jumps up.
  It's a time saver, and in a way it's like our own special code...for...well, I guess some of the kids take it as a code for encrypting love notes....

  Love notes, eh?  But it's not Valentine's Day!  True, but in third grade, every day is an occasion to write a love note.  Or a kind of complicated "You're going out with her so I'm going out with him" note.