I did this unit several years ago. We went to the official website of the Cave of Lascaux. You can navigate through the cave and check out the cave art together, so cool! Here is the website if you are interested; http://www.lascaux.culture.fr/?lng=en#/fr/02_00.xml.
This was a scratch art that I did with my 4th and 5th graders. It is actually a tar paper also found at Lowe's or Home Depot, from the roofing department. I believe one roll was enough for all 200 plus kids. I love this project, but plan for significant prep time and cross your fingers for good weather. You will need 8-10 cans of spray paint to get good coverage. Do yourself a favor, get the spray paint with the wide button. The first time I did this project I did not, and I had blisters on just about every finger tip (ouch!!). This may sound a bit scary, but students actually scratch with nails, BIG NAILS! I have done this lesson several times, not with just cave art, over the years. You just have to make if very clear of your expectations, one wrong move and they don't get to continue. Instead they get plain white paper and a pencil. Not once did I have to do more than just make that threat. They don't want to be "the one" who misses out on getting to use a nail to make their masterpiece!!