If you are unable to download Microsoft Expression Web to your laptop or home computer, you could build your website with one of the following web site builders.

They - are free for the small website you will be building,
        - will not put advertisements on your site,
        - will host or store your website for you on the internet for free and give you your URL (website address.)
        - just require you to have an email address and make up your own password.

www.webs.com/ ,

https://www.yola.com/ ,

www.weebly.com/ ,

www.snap.com.au/‎ ,

https://sites.google.com/ ,
 

www.kafafa.com/ .

You may not be able to access and add to your website from school, as externally hosted websites are blocked.

However you can do your research and writing at school, plus collect and make ready any pictures or diagrams you need.
You can then upload these to your websites from home.