some more suggestions:
- basic organization skills, since a lot of schools are using computers for homework now. like learning how to group things together in folders, put things in their respective libraries (Documents, Pictures, etc.), and so on. easy to lose assignments otherwise.
- how to put in a USB and safely remove it. they're most likely going to be using them a lot, so it's worth mentioning.
- i agree that it may be too advanced as well, but honestly slojanko's suggestion of learning the basics of anti-virus, ad-block, and firewall stuff somehow would be really good. i think even just a very basic explanation that it keeps the computer safe from getting sick may prevent some serious issues later on if they never really learn elsewhere? idk.
- how to install/uninstall software from the internet safely, perhaps. as in, how to download things, maybe some pointers on avoiding those shifty download sites, how to get them to install by clicking the .exe, and how to get to the "uninstall program" list in Windows (idk how it is for other OS).
im not sure how to make this not-complicated, but its a useful skill for anyone who is going to be using a computer like...at all. this way they won't need to ask for help every time like my dad does, or download from shady sites like my brother (who got a virus once b/c he just assumed all minecraft downloads were the same and it was ok to re-download it from any link that popped up on google). though this last one kind of falls into internet safety already mentioned.