Writing on the web is not the same as writing for print media
Unfortunately much of the web started life as paper information. If you are starting webpages from scratch, you can do better, and the paper based information you produce will benefit.
Tips
Do links say what information you'll find if you click on them? What information will your audience want? Can your audience tell where they are in a set of pages? Remember that, using Search Engines, people can jump to any of your pages from anywhere, not just the one you think is first. Can they escape to the most important local page (eg, the School's homepage)? Is important information loaded in pictures some people can't see?
These themes are sometimes called the 'Information Architecture' or 'Useability' of a site. They absolutely control how often people return to your site. Beauty has nothing to do with it.
Reading from computer screens is 25% slower than print, and more tiring because of the angle your eyes travel across. 80% of people therefore scan webpages. Use headlines like the one above this paragraph to help them locate their information. The School pages pick out the most important lines and words with STRONG and EM tags. Use paragraphs, lines, and lists to break up text.
Aim for half to a third of the text you would normally use. Don't use flowery or self-important text. Make the content or conclusions of a page obvious in the first paragraph. Split long pages up into themed pages, and give them an index page which is explicit about the information you'll find on each.
Minimise the number of pages with date and address information on them, and reference those pages when you want people to see the information. For example, use 'my diary' as a link to a timetable, rather than putting 'The dates of important events for Jan 2005 are here' on each page. You'll only have to change them all the next year if you do. Don't put 'last updated on' dates on webpages. Even if information only needs updating once a year, a 'last updated on' date of 11 months ago looks bad.
If you've written text for your page, go through it and try and cut out 50% of the words. For example, one of the sentences above started out as "You should rewrite information in an 'inverted pyramid style', that is, you should make it explicit what the page is going to say, and give away the 'ending' at the top in the first paragraph", after a bit of cutting, it's down to... "Make the content or conclusions of a page obvious in the first paragraph".
Go on to learn about designing webpages.