Writing is one of the most important skills there are in this world, perhaps only following the critical skills of reading (which is kind of crucial if you want to understand what you are writing) and social skill development. In truth, trying to rank the basic skills in some sort of hierarchal fashion might even be a waste of time, since they work so interconnectedly with one another in one’s daily life. But learning to write might actually be special in that, other than the reactive skills of socialization, reading and most math, writing allows a person to go beyond merely reacting to and consuming information, and into the realm of actually producing something original of their own. Some people have speculated that the ability to produce is far more important than the ability to consume, because it means that a person is contributing actively to the world instead of merely going along with what everyone else is doing.
When a person learns how to write, there is a lot that they have got to think about. First off, they have to be able to decide what it is that there are going to be writing about in the first place. Without that decision, the entire thing is just going to veer into the realm of nothingness. After all, it is extremely difficult to stay on topic if you do not even know what your topic is in the first place. Of course, this is not the only thing that one needs to think about during the writing process.
Writing is also great to learn because it forces a student (or really, anyone) to consider whom they are writing for. With a different audience, different structures and words are necessary to use, in order to express the concepts in question in a way that the ultimate reader is going to understand. If a person considers who their most probable audience is going to be before they get started, it is great for helping them to think critically about how this particular subset of individuals thinks, and what they think about.