In Brief: 
Students play the favorite American card game, War, using rhythm playing cards instead of the familiar king, queen, ace, etc. Two students each turn over one card from their pile. Whoever has the largest value card wins both cards. When cards are the same value, there's a war, and the stakes become higher
Articulate the relative values of notes and rests
Prerequisite Concepts: 
Fluency with the relative values of whole, half, quarter, eighth and sixteenth notes, dotted notes and rests
Teacher's Role: 
Demonstrate the game, and while students play, assess and assist when needed
Play for as much time as you have. Good game for a quick review