As students progress through elementary school, learning correct pencil grasp comes from teacher instruction and watching those around them. However, there are students for which a correct grasp around a writing implement is difficult to obtain. Oftentimes you will see these students use a "fisted" grip, or their fingers will overlap each other as they try to write. Another concern I have seen is either having too tight of a grip or too loose of a grip around the writing implement. It's important to correct the incorrect grasp because it will cause tiredness in their hand while they write and their handwriting will suffer. Until students are of the age when they can use a keyboard with success, handwriting needs to be worked on. When students are young, even preschool-aged, one of my favorite ways to correct an incorrect grasp is to use a claw pencil grip. These specialized pencil grips can stretch to go on pencils, pens, markers and crayons. They are formed with three cups that hold the thumb, pointer finger, and middle finger in the correct positions around the writing implement. "Claw pencil grip" can be searched on the internet should you be interested in finding one to purchase or learn more about them.
Happy Writing :)