Trial sites on Adobe BC are free and you only pay if you actually host a domain URL of your own using one of their plans. Basic sites should not be a problem for Year11 girls to move to Adobe BC however e-commerced sites require a lot of learning and I would avoid trying to teach this to beginners at the moment. I would also recommend using a responsive layout such as Bootstrap3 so your websites work on all devices. It's free to download and use,
http://getbootstrap.com/