I’m 25 and I’m going to be teaching a 9th grader about web development. I hope to get him started on HTML/CSS and quickly move into PHP/MySQL. I’m self taught. I’m looking for materials/resources that would help. Sites that have videos and perhaps assignments/tasks would be great!
One assignment I had my students do was mock up a Newspaper page because it teaches them the different sections of a page. Later, you can revisit that page with them and teach them how to style it with css or lay it out with a grid system (www.960.gs) or additional css rules.
Also, its wonderful you are starting him at such a young age. He will have plenty of time to develop the skills you show him out.