So, why use Publisher in schools? We can't think of a reason, either - that's why we don't bother. The communication section of the National Curriculum is done to death already, and is probably the only part done in a cross-curricular way, so students get plenty of practice at laying out documents.
Publisher doesn't do anything that Word can't do, and in most cases Word does it better. Furthermore, Publisher has all the wizards that let students fool teachers into thinking that they've laid out a page in an attractive manner, when all they've done is put a bit of text in template.
Lots of schools use it, though, so maybe we're missing something. So if you use Publisher for a reason other than because "the students like it", then contact me with your suggestions at!
Powerpoint, on the other hand, we're almost warming to. Although it's still mostly communication, you could argue that there are some quasi-control elements involved, although we'd argue that you'd be better off teaching students to create web pages, allowing them to sequence and refine their HTML tags.