Why is Writing important for an EFL teacher?

I am sure that writing is relevant for an EFL teacher, because it's an important skill that give us many elements to improve the English Language. With writing students can express their feelings, their thoughts and points of view about something. Through this way, teachers can determine which are the weaknesses that have their students at the moment to write. Of course we know that if we have a good writing, we have a good speaking.
What is the best way to teach writing to children? To teenagers? (Provide examples and references)
It's necessary teach writing to children, and teachers need to motivate them. They should prepare dynamic classes, because the students will be delighted to participate. For example: - Activities where students can express their thoughts and then, read them. - Writing essays. - Creating stories of different topics. - And the best way, using the thechnology through blogs, web sites, letters, etc.