Here's a tip worth checking out. I just found a treasure chest full of writing resource articles covering everything from sentences, paragraphs to essays. What more could a person ask for in terms of free help for parents struggling to teach writing.
Below are a few that I found particularly helpful but check back frequently to the Time4Writing site as they are adding articles on a regular basis.
Step-by-Step Guide to Writing an Essay
Paragraph Writing Secrets
The Writing Process: The Steps to Writing Success
Descriptive Essays: Tips for Writers
Narrative Essays: Tips for Writers
Persuasive Essays: Tips for Writers
Expository Essays: Tips for Writers
Types of Essays: End the Confusion
Understanding Writing Prompts
Writing Can Be Fun: Tips to Enhance Your Child’s Desire to Write
Writing Prompts That Inspire
Writing a Better Book Report
How Graphic Organizers Help Students Master Writing
How Writing Rubrics Improve Writing
Essay Writing for Standardized Tests: Tips for Writing a Five Paragraph Essay
Four Types of Sentences and the Effect of Punctuation
Let me know if you come across anything as rich as this list!