How do I prevent changes to home screen icons and arrangement?

I teach elementary school and I'm looking for a way to prevent my kids from making changes to the icons on the home screen/s. This way I can establish how each of them will look and they will remain as such (arrangement and folders). When an intermediate kid moves an app icon from one screen to another, or moves it into a folder, my kindergartners are completely lost. So I need to lock this ability down if possible. This is for iPods running on 6.1.6 and unable to upgrade any further due to their physical hardware.

Thanks!!!