Here is a little fun improvisation lesson that you can use to teach syncopation.

You will be using this MP3:  Syncopa

Make sure your speakers are on. 

Chant the rhythm below with your students: sync-o-pa, with the rhythm being an eighth followed by a quarter followed by an eighth tied to a half. Put this rhythm on the board after they have successfully played or chanted it.

Have your Orff instruments set up in C pentatonic. Demonstrate your sync-o-pa on any pitch and have the students echo. Start the MP3, Syncopa, and play a few measures yourself. Let one at a time try playing with the track. 

Options: Play one chorus using a different rhythm pattern, then go back to the syncopa on the next chorus. Play  the rhythms of fruit names, apple, peach, watermelon etc. Play the syncopa rhythm as a group, calling out which bars to play. Try an E, D, C pattern for instance, with the syncopa pattern on each bar.