There are special HTML tags for adding forms to websites. You can use them to request information or to run competitions. An interactive form requires that the information logged is processed by a "script", normally held in the cgi-bin (the folder that holds applications that work in the background to process information). Although many basic web hosting services don't permit you to maintain your own cgi-bin, most do place one or two basic scripts there on your behalf. At the very least your service provider should be able to link you to a "form-mail" reader. This is a script that will read the completed form, and return the information to you as an e-mail.
You could also use a simple form for a questionnaire or poll, providing you are prepared to process and report on the replies. Alternatively, you can fetch some ready-made HTML that will insert an interactive poll on to your site - ideal for running an instant YesNo referendum. (Try Alx's Free Web Poll at www.alxpoll.com).
With so many other enticements online you cannot expect visitors to keep returning to your site unbidden. A good way of tracking your regular audience and of prompting them to revisit to see new features is to set up a mail list. A technically minded school website manager, with access to their own cgi-bin, would be able to maintain their own list, but there are easier ways of doing it. ListBot (www.listbot.com), for example, will send you a few lines of HTML to add to one of your pages and, hey presto, you'll have a sign-up form. Once people have signed up and joined the list, you'll be able to send out an e-mail shot alerting them to new additions to the site. ListBot will manage the list and send the e-mail to everyone for you.
In time a significant amount of material will build up on your site and a search facility will help people find what they want. As with the mail list, it is possible to set this up yourself, but free services such as Freefind (www.freefind.com) will robot your site each week, index it, and provide you with a search box and button. A handy and useful feature.
Password-protecting an area of your site can help make your visitors feel special. Parents in particular may well be reassured that some parts of the school website are reserved for the school only. Protecting pages is extremely simple and entails loading two short files to your site. The first (.htaccess) is placed in the directory you wish to protect; the second, a simple list of usernames and encrypted passwords (.htpasswd), is loaded to the main directory.