I have a kitten whom we found as a stray and have since taken her in. She has lived with us for a little over a month now and has always been excellent about using her box. Within the last few weeks, she has this new habit where she gets her litter and scoops it with her front two paws and throws it outside of her box (it's seriously the weirdest thing to watch). Since she is so young, I want to break this habit ASAP, especially so I don't have to keep vacuuming so much. Any advice? Her box has fairly high walls, and she is a very intelligent cat and has plenty of other things to keep her busy.
The cat is doing that because it considers the litter box too small.
You could try using a hooded litter box, but that is risky, because if she decides it is hopelessly small, then she will start peeing outside of it.
The only reliable solution is to construct a BIG litter box. By big, I mean 30 inches by 24 inches by 6 inches.
If you have only one litter box for her, I suggest getting a second one. Many cats prefer to put their two different kinds of droppings in different places (one of my cats really first pees in one box then right afterwards moves on to the other one for his other business.)
Maybe cleaning the box more regularly would help too (at least two times a day).