Children can work with simple numbers worksheets from quite an early age and you will have greater success in getting them to work on the worksheets if you combine that learning work with something practical, or at least something they enjoy doing.
There are many more worksheets available. They vary in complexity of the activity depending on the age and grade level of a child. At a young age, kids are first taught to write letters in print only. When kids reach the age of eight to ten, they are taught how to write in cursive. They may find this quite difficult and boring at first. But one fun way to teach them this is to use worksheets also.