before with for
As the class period was about to end, I asked them to  check  the
floor like I do every period and thanked them for picking up any garbage  even if  it wasn't theirs.My entire class disappeared; they each disappeared instantly  under  their desks to pick up those annoying tiny pieces of paper
that  fall  so easily from notebooks.One girl made a (an  comment  that I later used with my other classes:" Her job might be to clean the room, but she shouldn't have to clean up  [MASK]  us.There's a difference."