Be a Math Ninja: Practice the facts in centers and guided math groups
Here is a great way to get your students excited about learning math facts. We should emphasize composing and decomposing numbers, flexibility and confidence. Here is a school that is doing just that!
I would have the students working with each other to get efficient and fast. They are only really competing against themselves but practicing individually, in partners and in groups. I would also have them do some practice at their level with me in guided math groups. Remember that the CCSS has 3 levels of efficiency (see the math progressions operations and algebraic thinking p.6)