The best way to get primary school kids interested in writing is to spark their interest in reading and storytelling. The earlier this can be done, the better their interest will be. Children are naturally curious and enjoy being given the opportunity to be creative and exercise their imaginations. Writing is a natural outlet for expressing their inventive thoughts.
Children who are readers are more likely to become good writers, but even those who are just learning to read enjoy having stories told to them and making up stories of their own. When given the opportunity to share these stories and entertain other students, kids can then experience a sense of pride in what they have accomplished. Though some kids are shy about sharing, most are excited to show off what they have done and the self-esteem boost they get from doing so is what will help them feel confident about writing and sharing more stories.
It is important, particularly with creative writing, that more emphasis be placed on story creation than on spelling, grammar and punctuation. Those things can be addressed at a later time after the stories have been completed. (Think of it as reverse engineering.) If students can get excited about writing early on they will be more likely to maintain an interest in it throughout their school careers.
Children as young as Kindergarten students can be introduced to writing at the very basic level by creating their own alphabet books. As they learn simple words they can be encouraged to create more books. They can also orally make up stories collectively as a class that the teacher can write down. These stories can be bound in simple books that the students can take home and read with their families.
Second grade students can work as a class or in teams and take turns adding parts to round-robin stories. Most children love to draw and will want to create illustrations for their stories. As their writing skills improve they can be encouraged to create stories individually. Stories can be a single paragraph or take up an entire page. The important thing is that the students learn how to give their stories a beginning, middle and end, and that they at least answer the who, what, and how questions of storytelling.
Making up their own stories is only one way to get students excited about writing. Exercises that allow students to write reflectively, particularly with students who may be having behavior issues, allow them to see how writing can be a useful tool that helps them to put the things that happen to them in perspective and even to feel better.
Third and fourth grade students should be able to interview each other and write short journalistic style stories that allow them to get to know each other better. As their skills improve they can interview family members or neighbors and learn about oral history.
As primary school students begin to think of writing as something that is useful and has value to them it will become increasingly easy to foster their interest in it.