All students can write, if we let them. The key, I think, is poetry.
As a poet myself, I have a love/hate relationship with schools. For the most part, schools have been a place for me to learn and grow. They've given me the chance to find readers of poetry and to connect with the poets of the past. I have found almost all my poetic brethren (dead poets who speak to me through their work) within a classroom setting.
However, because I am a poet, I am always searching for ways to change language. Schools are often a place for a certain sort of rigid language instruction, which can make them hostile environments for poets. Grammar and persuasive argument are essential skills for any student. But if someone is telling you that there is a set and finite way to construct a sentence -- and you're a poet -- you will naturally get a little annoyed. And you will be justified in feeling this way, because it's simply not true.
Nothing is more important to the future of humanity than the freedom to make new ideas. I would argue that the act of writing poetry is important for the creation of those new ideas. In her essay "Poetry and Grammar," the great American poet Gertrude Stein wrote:
That is the reason that slang exists it is to change the nouns which have been names for so long. I say again. Verbs and adverbs and articles and conjunctions and prepositions are lively because they all do something and as long as anything does something it keeps alive.
Supporting poetry in our schools is essential because it engages students' thinking and it keeps language alive. Over the past 14 years, I have worked as a teacher in a variety of educational settings. I have found that all students can write. And one of the surest ways to awaken their love for language is poetry.
The 60 students waiting patiently to get into one creative writing section at an elite private college where I taught loved writing poetry. The 2 year olds I used to teach over a decade ago in a wealthy day care loved poetry, too. Even in their pre-writing state, they recited poem after poem for me, and I wrote each one down for them to then illustrate. At an underserved elementary school, I read Merwin, Sexton, and Whitman poems out loud, and the 5 year olds in in the class loved to bounce around the rhythms and the sing-songy rhymes, along with the slanted ones. It was the music of poetry that they loved. The music of poetry is a delight for the mind.
Every outstanding essay involves meticulous word choice and sheer aesthetic prowess. Poetry teaches students how to do this.
A lot of people argue that poetry is "difficult" or that it has no real value for children's future. That's just not true. If you think poetry isn't important to your students, you are not listening to them. You are not noticing the headphones in their ears, blasting poetry to soothe their walk to class. You are not thinking of them in their rooms at night, writing down their experiences. It may be that you are defining poetry too dogmatically.