If your teachers' lounge has a blender, use it. If not, invest in (and bring to work) a Magic Bullet. Put a few ice cubes, 1-2 cups of spinach, and a chocolate shake (IP packet, liquid, or ProtiDiet) and whip into a shake. You can't taste the spinach, even though it'll look green. Obviously, add some water to the mix if you're using a dry-shake mix!