My classroom is very small and so painting is done at the children's desks. I find that covering the tables with newspapers is time consuming and without fail, children will manage to rip them or pull them off. I used to dread anytime I wanted to paint. I now cover the tables with shower curtains. You can find these selling for approximately $2 and they are easily cleaned. You can also pay that little bit extra to get thicker plastic curtains or ones printed with attractive designs. Another benefit of using plastic is that artwork does not get stuck to it as it does to newspaper. The students love to help setting up the classroom for art too.
Shower curtains are also great when you are having group time and are working with messy materials e.g. leaves, science experiments, water. You can even fold these up and take them on excursions, which are great for those times the grass is that little bit wet or the ground is really dirty. You can also use large tarps for the same purpose.