D (age 9), received a couple Ja-Ru DinoWorld Fossil Kits last Christmas. They are inexpensive, grocery store aisle finds, but turned out to be some of the best fossil kits we've ever tried. Each kit contains a small egg shaped "rock" from which to excavate the tiny plastic bones of one of six different types of dinosaurs.
There are seven bones (1 head, one body, one tail, and 4 legs) for each dinosaur. The bones snap together into a skeleton, and fit into a stand that comes with the kit, along with a digging tool and brush.
What D liked most about the kits was that the material the the bones were buried in was perfect for excavating, more like soft sandstone, or maybe even a sandy chalk, than the brick hard substance so many of the toy fossil kits contain. It reminded me vaguely of dried Oobleck - the non-Newtonian liquid you get when you mix one part water to two parts cornstarch.
No-one sells Ja-Ru toys in our area, and since there are only six different types of Dino World kits to choose from anyway, I decided to try recycling what we already had by dropping our dinosaur skeletons into a paper cup filled with Oobleck and a couple of teaspoons of play sand.
To shake things up, and increase the difficulty, I dropped the bones from four different dinosaur skeletons into the same cup (after taking pictures of them sorted out correctly according to skeleton, for later reference).
That, in itself, proved to be a fun game for the children.
If you hold your finger still for too long in the liquid, too much of it will liquefy, and you will release already buried bones. Or, if you pull your finger out too quickly, the liquid will not solidify, and the bone will float right back to the surface.
...except that even with the picture aids, I'm not entirely sure all the skeletons were assembled properly. There may have been some mixing and matching of leg bones...
...and despite a thorough search, one tiny skull was never recovered (it's possible there might have been some pillaging and theft by a rival museum's team). Luckily, D had another skeleton, that was missing a tail, to borrow from - creating a new dinosaur (tristegosaurus?) in the process.
That's paleontology for you.
It's great to be a homeschooler.