Kids tend to be really creative inside the home when they are young. Their creativity can be seen through a lot of ways, but the most deplorable show of creativity is when you see them draw on the wall with crayons. This isn't on at all cost, because cleaning crayons from the walls is an extensive task that requires a lot of cleaning.
So, instead of giving your kids an earful when this happens, you should be more concerned about clearing the walls. The walls ain't going to clean themselves, so all you need to do is to get some toothpaste on you. The toothpaste can be used to rub on the affected area and you will be fine later on. Just rub the toothpaste and see as it does its magic on the walls.