Chromebooks are great - they run on the super-lightweight operating system Chrome OS, which isn't as demanding on your hardware and can be set up in child safety mode to give you more control over your kid's browsing, perfect for younger users.
Chrome OS supports Android apps from the Google Play Store too, which means that if you get a Chromebook with a touchscreen it can be effectively used like a large phone or tablet.
However, it's important to note that Chromebooks aren't really for gaming (unless you get a game-streaming subscription) and Chrome OS doesn't support a lot of software that runs on Windows - of particular note here is that if your kid needs to use specific software for school, it's vital to check what operating systems it can run on.