This is a great way to start a formal piece of writing, or, it stands alone as a great brainstorming exercise. Many serious writing tools have outliners built into them. Most people who use these tools avoid the outliners. This is a pattern learned before outlining was electronic and forgiving. Outliners are excellent tools for making and categorizing lists.
Some students find the linearity of lists and outlines hard to see and use.
Use paper and pencil or a program like Inspiration to generate ideas and connections between ideas. Inspiration allows you to move back and forth between graphical and outline views of the same information. Other Ideas to Generate More Writing Make whatever you are writing or your students are writing meaningful. Take the emphasis off of skills, put it on content. Experiment to find appropriate tools.