The other comments have been on the mark so far about usability and teaching solid principles, so I won't rehash that. But keep that in mind along with the rest of this.
The important thing that you learn in high school isn't this language (programming or human), or that equation, or the other literary work. It's how to get along with other people. A web development class is a great opportunity to teach this, because of how web development goes.
I'd say probably three teams, according to the segmentation above-- a graphics team, a client-side team, and a server side team. Hopefully someone on the server side team is brave enough to take a shot at setting up a linux box with apache and php, if not the teacher could provide the tools (with your help of course).
Have them identify the scope of the project, plan out the stages needed to get there, and then do the thing. Will the end result suck? Probably, but think of it this way: you'll have saved the world from the first websites that each of them individually could have created. :-)
Make sure that their final site is publically accessable too! This is important. There's no point if no one else can see it, which is one of the basic tenets of the web. Perhaps suggest they do a site for the school, like a student government site or something. But don't force the issue-- if they want to do an X-Men fan site, let 'em.
The point of all this of course, isn't that anyone necessarily remembers any specific technology they learned in this class. Some of them might, but they'd have learned that stuff anyway. The point is that the web is all about collaborative work, as is life, and that's what they should be learning. Plus, that class would be cool as hell, and what teacher doesn't want to have the coolest class in school. ;-)
Not the real rusty