There's no need to pay someone to build your site for you. Really, all you should be paying for is your domain registration and web hosting
You can design your site yourself. I use Front Page for mine, which works very well.
I would suggest against that. Website is a great source of recruitment, well not so much for kids, but for adults it is. A good webdesigner is the way to go, homemade sites always look homemade and rarely get any exposure.
You should have someone that understands web programming, can make you more then a static page and knows how to get search engines to pick it up.
Pages should be interactive, at a minimum you should have a registration form online.
What it really comes down to is that if you want a professional image of your school given by your website, you need a professional to develop it.