I have heard that wet newspapers were at one time used by the FBI forensic labs. Now I'm sure they use ballistic gelatin. You can by ballistic gelatin... Cabela's used to sell it or go to your local gun shop and ask them to order some from Brownells orChattanooga Shooters Supply. You can alsobuy it online.
Check out this website...
http://www.myscienceproject.org/gelatin.html. This websitehas a couple ballistic gelatin recipes. If nothing else, it'll give the kids something to mess in.lol
More websites: recgun.com/Sources/XD3.html.
gelatininnovations.com/pages/ballistic.html.
pyramydair.com/blog/2007/02/how-to-make-ballistic-gelatin.html.
firearmsid.com/Gelatin/Ballistic%20Gelatin%20Report.pdf. This has some good information about the physical aspects of testing.
And don't forget to do a search on you-tube, they have some videos on how to make it.
Have Fun-