Some writers only define their objectives after they begin writing a piece. Like me, they use writing to clarify thinking and discover their themes. Others work from detailed outlines with all content defined in advance. Some authors edit for content and mechanics at the same time. Others worry about content first and address mechanics later.
Many famous authors dictate everything and leave the transcription and punctuation to someone else.
Others have to work with certain pens and specific types of paper. Many could not produce anything without a word processor. Among the incredible variety of real writing processes are be tips and hints that will appeal to you and work for your kids. Brainstorming heads the list. Let's say your homeschooler wants to enter a non-fiction contest but cannot decide on subject.