Woo! A SUCCESS! Well, okay, maybe you will notice the top left one has a hole blown out of it - but all in all the whole batch of rattles survived the firing to be happily rattled and painted. The kids were stoked about the end result.
See my previous post about the prep and my PDF how-to that I made for the kids explaining how to make a clay rattle: http://scarymaryart.blogspot.com/2012/01/clay-rattles-with-5th-grade-coming-soon.html
P.S. Cultural connection to Maria Martinez (an ideal connection would have been a coil pot but the kids informed me they have done "SO MANY COIL POTS. UGH" so I switched it up :)