If you're going to introduce your music class to the Boomwhackers, then what better way than to have them do a bit of research!
This is a simple first step for your class, and points them in the right direction. More worksheets in the series to follow.
Note: You may have to explain the concept of sustain or sound that echoes or lingers even after you strike an instrument.
Research observations may be varied but you can have a general discussion and steer the class towards the outcome you want. Eventually have them analyze their response and see how it differs from your own.
This is a high quality pdf file that can be printed in A4 landscape mode.